40s cab demensions

Hi all.can anybody tell me where I can find some mesurements for a 40s chevy p/u cab? I need to know the length of frame I need under a cab. I am building a custom 2 by 3 frame. I want to use a frame kick up in front of the cab and Z the frame just behind the cab, so how much frame do I need under the frame? The rod will have a 4 link rear and a sring behind drop axle in the front. A 350 / 350 combo for motivation.
This is my first atempt at building this type of rod and am looking for all the info I can get.
thank a bunch
Rob [email protected]

 

My 40 GMC is 54 1/2" (±1/2") from the firewall to the back of the cab.
Chevy's supposedly the same cab but the front sheet metal is different.
GMC is longer to the core support because the GMC engine is longer
Reason for giving the tolerance is when I chopped mine, the contour of the cab B pillar area was 3/8" different from side to side when I thought a template it might be a good idea.
Seems they didn't bother at the factory..
They may all be fairly different.

I recommend measuring the body you are using for confirmation.

Welcome to the HAMB!

 

thanks. that is a great help, I am drawing up a set of prints for this build and wanted to check with other builders. thanks again
Rob

 

My 39 Chevy is 54" also. I didn't look for the 1/2. I'm sure it's here somewhere. And, no, they aren't absolutely symetrical from side to side.

 

Good on the confirmation. Scotty!

That's because you're measuring on the short side of my stated ±1/2" tolerance.

Also, there is a slight curve to the back of the cab so it depends on where you measure.
Since he's making a frame the cab should fit on it'd be a shame to make it a 1/2" too short.

I'd like to add that though the '39 cab is the same as the '40 but with a different dash board, in '41-'46 they bumped the firewall out a couple of inches into the engine compartment for that much more foot room and will make those measurements about 2" longer.
It's easy to tell the difference.
The '39-'40 have 2 vertical reinforcing corrugations on each side of the engine depression while the '41-'46 have "X"s stamped in them.

 

make it out of 2x4 box and you won't even have to channel it!

 

just remember if you zee the front, you can hide the zee under the cab, since the floor board is slanted. I'm building a 45 gmc, zeed 6'' channeled 5'' running leaf springs front and rear.