1968 C20 to C10 frame differences?

[KevinK7]

Will existing C20 parts bolt right up to a C10 frame?

I'm relatively new and did a number of searches, yet still not 100% sure on the differences of the actual frames themselves. (If there are other threads on this, please post links)
I know a C10 is a 1/2 ton and C20 is 3/4 ton, I know there are differences with the rear axles, lower control arms, etc. However with the actual frame itself, what's different?

I have a '68 C20 longbed (396 4sp) that I plan to lower a bit and go to shortbed. (also going to 5/6 lug, disc brakes, etc.)
I could cut/shorten my existing C20 frame, but I have access to a 68 C10 shortbed frame only. I'm going to disassemble the truck either way but I'm hesitant to cut a perfectly good frame, will the '68 frame work?

I've looked at Early Classic's spindle kits (that work with C20 control arms) which I will most likely go with. Then in the rear, I realize I will have to change out the rear/axles (going to 5 or 6 lug).

So, ...Will the existing C20 parts bolt right up to a C10 frame? and/or is there any reason to just go for all C10 parts?

Thanks in advance for any information,

Kevin

[Coley]

The 1/2 ton frame is smaller than the 3/4 ton frame for load/duty purposes.
In that, you will find that the 1/2 ton frame is not as 'high' (vertically) as the 3/4 ton frame.
To my knowledge the outside 'cross' dimensions and mount points relative to the cab, fenders, box, bumpers, etc are the same.
So think of it this way....if you can envision a 2x4 vertically on edge.....think of that as the 1/2 ton....then the 3/4 ton would be a 2x6 vertically on edge....if that makes sense.

Coley

[KevinK7]

Thanks for the reply.
I actually thought the 1/2 and 3/4 where the same height, where the 1ton was taller.
Still wondering though, will C20 components bolt up to a C10 frame?

[projectking]

1/2&3/4 are basically the same height, the 3/4 has larger doubling plates in it. Everything will bolt up assuming you have 2 leaf or 2 coil spring trucks. Not too sure if you want short 5/6 lug truck why you are considering an 8 lug chassis though(unless it’s a bare short frame)?

[projectking]

C10 115 C Blazer
C10 127 6.04" height 2.53" flange width 0.156" thick 2.98 section modulus

C20 127 6.11" height 2.46" flange width 0.194" thick 3.71 section modulus

C30 133 C20/30 Longhorns 7.20" height 2.77" flange width 0.194" thick 5.05 section modulus

C30 157 8.18" height 2.97" flange width 0.224" thick 7.29 section modulus


K Blazer
K10 115 6.02" height 2.71" flange width 0.141" thick 2.70 section modulus

K10 127
K20 127 6.09" height 2.75" flange width 0.186" thick 3.48 section modulus

[michael bustamante]

the c20 frame Is taller in the c chnnel so I don't think most half ton components will fit. like the auto tranny crossmember will only bolt on the bottom half the ears that bolt to the top of the C in the frame wont reach.. I don't think an steering or suspension components will just bolt on

[KevinK7]

Originally Posted by projectking

1/2&3/4 are basically the same height, the 3/4 has larger doubling plates in it. Everything will bolt up assuming you have 2 leaf or 2 coil spring trucks. Not too sure if you want short 5/6 lug truck why you are considering an 8 lug chassis though(unless it’s a bare short frame)?

First, Thanks for the replies.
The truck I have is a '68 C20 longbed, coils in rear (that has the 8-lug).

The frame I came across is a 68 shortbed frame (frame only). I would consider swapping IF that was a feasible (or even possible) route to go.

From the replies, it does appear there are 'some' differences leaving me (for the most part) with two options:
1.) Cut/shorten my existing C20 frame and change what's necessary to drop and switch to 5 or 6 lug.
2.) Find a complete C10 frame with all it's suspension parts and swap in drop components.

My preference would option 1. (The only drawback being I cut the frame, but I can live with that if it gets me where I want to be).

I am not building a show truck, my plan is to keep the original patina, lower it, add some wheels and drive the thing.
As for going to 5/6 lug, that is by no means a 'deal breaker', I'm just trying to increase my wheel options. With that said, if I want to go disc's up front and lower (ie. Early Classic's C20-C10 drop spindles) I believe I need to go 5 or 6 lug...??
Maybe I don't even need ECE drop spindles and suspect with swapping out the C20 lower control arms (and?) I could use other spindles to gain disc brakes) and lowering springs only). Just to give an idea on how much drop I'm looking for, I believe I am in the range of (about) 2-2.5" front and 3-4" rear.

I am open to suggestions on all of this... that's why I'm here

Thanks again,

Kevin

For the record, here's the truck as I got it...