Frame differences??

[68shortfleet]

I have two questions here
First, I have numbers stamped into the sides of each frame rail right behind the front cab mount.
Drivers side 3913179-291
7-11-103
Passenger side 3913180-291
5-8-101

My vin is also stamped twice on the top of the left rail, once right behind the gearbox, and again right under the middle of the cab.
Can anybody tell me what the other numbers mean?? Not the vin.
Vin #ce148z105085

The second question relates to the frame metal thickness. My truck is a 68 c-10 swb. Some previous owner cut a little off the front frame at the bumper mounts, trying to install a roll pan? I got some front frame peices from a 71 c-20 frame to weld on. I discovered that the front body mount was located in a different spot in relation to the bumper bolt hole. I also found that the metal thickness was different. c-10 was .160 thick, c-20 was .190 thick.
Were all c-20 frame thicker like this? Does this mean that a c-20 frame that has been shortened could actually be a stronger, better handling frame than a factory c-10 frame?

Thanks
Jason

[BigTex]

Good questions.

My truck project has a 1972 C20 frame that I may shorten. Where did you measure the thickness? I can measure mine for you.

[68shortfleet]

I am working with about the front ten inches of frame. 68 c-10 and 71 c-20. Could it be a change in the years? early frames were not as thick as later frames?

[68shortfleet]

I never really liked the idea of shortening or lengthening frames until i saw the writeup on this site about how to do it. I found it to look acceptible for me(not that i need to do it). I might full box that section of frame also. But now i find that the frame thickness is better than a c-10 swb. I really see no problem with a properly shortened c-20 frame now.

[kwmech]

I think those numbers are part numbers from the factory. I noticed the same thing on my 3 trucks

[Blazer1970]

Originally Posted by kwmech

I think those numbers are part numbers from the factory. I noticed the same thing on my 3 trucks

Yes, I would think that they are the part numbers for the left and right frame rails.

[68shortfleet]

That was my thought on the numbers also, kinda wondered if part of the number might be a date code also?

Anybody on the frame thicknesses?

[CPNEJR]

the 3/4 tons and one tons are supposed to have thicker frames to handle more weight that they are built for

[Green Machine]

The 69-72 1/2 and 3/4 used a thicker rubber cushion for the radiator support, the hole is larger in diameter, and the bracket is mounted lower on the frame to allow for the thicker cushion. I have always heard the frames were basiclly the same.