Sean - since no one else has responded yet, maybe I can help you out a little.

As for the frame, I don't know if a truck will fit on a car frame, but I do have a diagram of a frame in my gallery (just click the little picture of my truck on the left). Ours is an original 1941 truck (F100) frame which is the same as a 1940 so you should be able to measure your's to see if the measurements match up.

As for the individual parts, I think you would be better off searching for a whole truck rather than to try and put one together piece-by-piece. The original parts are hard to find and the aftermarket parts aren't that cheap.

As for the tranny, if you're using a modern engine, use a modern tranny - same with the rear, axle, etc.

Carlene