Chevy Truck frame(s)

[baddiesel]

I know this will sound like a dumb question, but I'll ask y'all & hang my head in shame. Is a 1971 Chevy C20 frame and a 1986 GMC 1500 (short bed) basically the same? I'm more concerned about width, not so much length. I'm attempting to put a 1971 body on a 1986 frame. I appreciate your info.....Thanx in advance.

[thirdstreettito]

Is the 86 a C20?

Is the 71 a short bed?

If so then yes they are "basically" the same.

And I use "basically" lightly.

[baddiesel]

The 1971 C20 is a long bed, and the 1986 1500 is a short bed. The reason I'm not so concerned about the bed length, is because I plan to install a stepside or fleetside shortbed on the '86 frame. I am concerned with the radiator support braket fitment/fender/cab fitment (eg width & length). Thanx for your response.

[Sammy]

If your worried about width. Yes they are different. Thats why the 86's had inside frame mounted gas tanks. Imagine the core supports/cab mounting would be different but that could be redrilled. If I'm wrong someone will tell us.

[90\87Formula]

Check these two links. They have some of the dimensions.
http://67-72chevytrucks.com/vboard/s...d.php?t=180770
and
http://www.chuckschevytruckpages.com/framespecs.html

[baddiesel]

Thank you Sammy. I feel certain there will be radiator support bracket issues. I thought about fabricating & welding steel tabs in order to implement this installation. The '86 frame is very clean & corrosion free!

[baddiesel]

Thanks 90/87 Formula. I was not able to save/print the jpegs from chucks chevy truck pages. I was trying to locate the specs on the '86 frame to make a comparison. Thank you again for the great info!!

[BLACK AND BLUE 67-72]

Yes they are different, the radiator support brackets are mounted in a different position, cab mounts are different and the bed mounts different.

[BLACK AND BLUE 67-72]

Talk to Mudder he has done this with his truck.

[Longhorn Man]

this is a swap that basicly will not work. The 67 - 72 frame is flat. The 73 - 87 frame is not flat.
A 4X4 you can make work by modifying the wheel base, and then making a custom body lift to make the cab sit as high as the bed. But a 2 wheel drive will look retarded with a body lift.
Not to mention you have a 131 inch wheel base frame that you wanna put a 115 inch wheelbase truck onto.
Also, a comment up there, the fuel tank is not between the frame rails on an 86, it is the side mounted one that got lotsa wrong publicity about 10 years ago of so.

[baddiesel]

Mr. Longhorn Man, I appreciate your info. My '86 is a 4x4 with 1 ton running gear through out. I believe you're 100% correct regarding the elevation aspect, this is going to be a tough, and very complex swap due to non-similarities of the frame. I can fab/weld cab mounts inboard or outboard. I'm having the most difficult time with the measurement and fitment of the distance from the radiator core support through the fenders, to the cab itself. That's a rascal to pinpoint exact placement & proper fit to make it look correct.

[BLACK AND BLUE 67-72]

Like I said PM Mudder on this he has pics and the info on how to do it, he gave me the info on it before my computer went to pot.....

[baddiesel]

Thanks Black & Blue. I'll go to the member's list and PM him.

[Longhorn Man]

I never noticed it was a 4X4... my bad.

[baddiesel]

I wasn't specific regarding what was what. I have a 1971 C20 body that I'm "renovating", and I want to install it on my '86 GMC frame. It has all the goodies in the driveline that I like, except it's very thirsty. I love my '71, just prefer my 1970 454 V-8 eng, built 700R4, NP-205 twin-stick, dana 60 front w/EZ locker, 14 bolt rear w/detroit locker. My '86 won't pass North Carolina's smog/safety inspection. But, with the '71 body mounted on top of that frame & driveline, it becomes exempt from inspections. I'm starting to think this is not feasable. I've worn-out a tape measure trying to analyze the fitment.

[BLACK AND BLUE 67-72]

No problem, anytime!!!!!!!!!!!!!

[Mudder]

It's not a big deal at all.. I will email you the info in the morning after you pm me your email addy.

[72 CustomCamper]

Originally Posted by Sammy

Thats why the 86's had inside frame mounted gas tanks.

73-87 had OUTSIDE the frame fuel tanks. 88-up they were moved inside the frame...

[og350]

if you need some more pictures my "redneck" neighbor put a 70 body on a 76 2wd frame and then made it a 4x4. it works but yes the front rad support mountis different and the rear cab mount had to be moved. i dont like how much gap is between the cab and frame. why not just use the 70c20 frame you have and make it a 4x4?
good luck!!

[Dooley]

Originally Posted by 72 CustomCamper

73-87 had OUTSIDE the frame fuel tanks. 88-up they were moved inside the frame...

The 87-91 R and V model pickups and chassis cabs had the fuel tanks outside the frame rails.

[baddiesel]

Mr. OG350, I believe it will be less work to fabricate & move sheet metal, than to modify & relocate an entire drive train that is already operational and in-place. My '86 GMC short bed also has a roll cage and rock sliders installed, along with a 14,000 lb winch on the front. If I could just relocate the radiator support, front fenders, hood & cab onto the '86 frame, I would be soooooo happy. I would also install a new wiring harness from scratch (custom marine grade w/breaker switches).

[Mudder]

Your information is on the way.

[baddiesel]

Mr. Mudder I received your photos. Thank you very much, you've got a PRIMO truck!!!

[72 CustomCamper]

Originally Posted by Dooley

The 87-91 R and V model pickups and chassis cabs had the fuel tanks outside the frame rails.

Yes the 87-91 heavy 3/4 and 1 tons still had the tanks outside the frame. The 1/2 and light 3/4 tons had them inside the frame starting in 88. The truck he is asking about is an 86. The person I was correcting was saying that they all had them inside the frame...

[Mudder]

As far as tanks go it would be the best to get a Blazer tank from the year frame you have and bolt it in.