C20 long bed to short bed conversion - questions

[69Tom]

I've seen plenty of long to short bed conversions done on C10s, but not a lot on a C20. I'd rather not move the forward leaf spring hangar if I don't have to.

Does anyone who's done this have any suggestions and/or drawings for the cutting area? Wasn't able to find much in my searches. This would be for a '74 C20.

Thanks.

[mongocanfly]

Are you referring to cutting the frame?...if so, I've done several and always cut them in the horizontal section that's under the cab and bed front..

[69Tom]

Cutting the frame, relocating cab mounts. Is the C20 long bed frame essentially the same as a C10? I'm not seeing a lot on the square bodies for this. Mainly 67-72 stuff.

[tinydb84]

On the 73-87 you dont need to move the cab mounts. The cuts follow the same as the usual c10 frame. Its usually in the straight section between the front spring mount and the back of the cab.

I believe it is 14 before the axle and 8 after but check a few other threads to confirm.

[SCOTI]

Long to short should require 14" removed from the area in front of the axle but behind the rear cab mount. That's what it took on the 67-72 lwb frame that's now under my swb '64.

Look @ the area on the frame rails between the front leaf hanger & rear cab mount x-member to give you an idea of the layout. Use the 14" & 6" dimensions as a starting point for removing material. Then, trim more off the rear of the rails if needed.

[69Tom]

Thanks. Found some info on another site. Looks like there is enough room to do a step cut there.

[mongocanfly]

thats where i cut mine...i just do a straight cut, and then flip the cutout section around on the inside of the frame, overlapping the welded section...thus boxing the frame

[kipps]

The only difference between the c10 and c20 frame, is the thickness of the metal. In all other dimensions, they're the same. The c30 went to a taller frame.

This also applies to the k10, k20, and k30 frames as well. The k10 and k20 frames are the same except for the thickness of the steel used.

[69Tom]

OK, got it. Thanks. Anyone have a good template for the step cut? 14" long, just curious how long you make the step sections.

[SCOTI]

Originally Posted by 69Tom

OK, got it. Thanks. Anyone have a good template for the step cut? 14" long, just curious how long you make the step sections.

When I did my LWB-to-SWB conversion, I used as much of that 14" horizontal surface for the weld I could since I don't weld for a living. Added insurance from my perspective. I also plated the outer side of the frame rail in that area using perimeter & plug welds after grinding my welds in the 'step' area smooth.

[69Tom]

Ah good idea. Thanks for the tip.

[SCOTI]

Originally Posted by 69Tom

Ah good idea. Thanks for the tip.

On my application (Truck-Arm rear suspension), the T/A x-member slides into the frame so I didn't want to box in that area of frame but wanted additional reinforcement. The welds inside of the rails were just lightly buzzed over for clean-up purposes. The outside rail surface was ground flush & then the plates added. Welds were plotted & done so as not to be on top of each other (inside of rail vs outside of rail).

I cut the rear portion of my frame as well for a different mod & did this similar plating arrangement. I eventually plated the outer portion of each rail from the trailing edge of the front cab mounts all the way back to the rear frame rail 'kick-up' for a cleaner visual appearance.

[69Tom]

Originally Posted by SCOTI

On my application (Truck-Arm rear suspension), the T/A x-member slides into the frame so I didn't want to box in that area of frame but wanted additional reinforcement. The welds inside of the rails were just lightly buzzed over for clean-up purposes. The outside rail surface was ground flush & then the plates added. Welds were plotted & done so as not to be on top of each other (inside of rail vs outside of rail).

I cut the rear portion of my frame as well for a different mod & did this similar plating arrangement. I eventually plated the outer portion of each rail from the trailing edge of the front cab mounts all the way back to the rear frame rail 'kick-up' for a cleaner visual appearance.

Thanks. For your cuts, I assume you used a sawzall? I'm concerned about the precision on the curved cuts with it. However, I'm sure it's possible.

[SCOTI]

Originally Posted by 69Tom

Thanks. For your cuts, I assume you used a sawzall? I'm concerned about the precision on the curved cuts with it. However, I'm sure it's possible.

4" angle grinder & cut-off wheel. I made the rough cuts w/extra material as a fudge factor. That allowed straight cuts & then going back w/a flap disc to slowly dial in my curves. I laid out the lines first for the visual guide & used a template for the curves.

[69Tom]

So while I'm on the subject, just confirming other things I need:

• 16 gal fuel tank
• parking brake cables (super excited to replace these - always a good time)
• front to rear hard brake line
• drive shaft shortened (is it going to be 14" or will it vary a bit from that due to change in angle?)

When putting in a new tank, I'm just going to replace the sending unit as they tend to start not working great after 45 years.

I'll also replace all rubber fuel lines, rear cab mounts, rear shocks (to match my new front Bilsteins I just put on) while I have the bed off.

Anything else I'm missing?

[tinydb84]

Not truck related but get a set of trailer leveling jack stands: https://www.amazon.com/dp/B083KJ782P...NsaWNrPXRydWU=
They will make getting everything level so much easier.

[69Tom]

Originally Posted by tinydb84

Not truck related but get a set of trailer leveling jack stands: https://www.amazon.com/dp/B083KJ782P...NsaWNrPXRydWU=
They will make getting everything level so much easier.

Ah, those ARE nice, compared to the normal floor jacks, which I'm sure shimming is going to make me curse quite a bit. haha.

[69Tom]

So next question, instead of having my drive shaft shortened (to the tune of $450 w/ new u-joints), can I just find a short bed drive shaft and save myself some money?

[tinydb84]

Originally Posted by 69Tom

So next question, instead of having my drive shaft shortened (to the tune of $450 w/ new u-joints), can I just find a short bed drive shaft and save myself some money?

You could. Not sure if it would be that easy to find. Not many c10s in the local yards for me. Plus you wont know if it is bent or anything until you get it to the shop.

My new shaft with everything was $350. It shouldn't cost that much just to cut it down.

[SCOTI]

Originally Posted by 69Tom

So next question, instead of having my drive shaft shortened (to the tune of $450 w/ new u-joints), can I just find a short bed drive shaft and save myself some money?

$450?? They're removing material not adding it

When I had the LWB C10 driveshaft shortened for my SWB 64 @ a local shop, it was less than $200 (trimmed to length, welded, balanced, & new front joints).

[smupser]

Check out these guys and their plates. I’m haven’t done enough research on long to short conversions but seems like they use existing holes for everything and claim it’s the easiest setup on the market.

Www.metaloxfab.com

[69Tom]

Originally Posted by smupser

Check out these guys and their plates. I’m haven’t done enough research on long to short conversions but seems like they use existing holes for everything and claim it’s the easiest setup on the market.

Www.metaloxfab.com

I actually bought a pair. He's located here in Phoenix. Looks like it'll be pretty easy.

[smupser]

Originally Posted by 69Tom

I actually bought a pair. He's located here in Phoenix. Looks like it'll be pretty easy.

Please keep us updated and let us know