I went out and measured my '37, it's the same basic setup as the newer trucks. The rear bumper is 7" higher then the front, so the it has a nose down stance. The garage floor is pretty level, bed rails are 4 degrees down in the front, running boards are 3 down in the front, frame is 3 degrees down in front. The drag link is 4 degrees up in the front, so it's NOT level by quite a bit. If it was level, it would be 7 degree lower in the front then it is now. The only way to level it would be to raise the gear box.
Point I am making, is it doesn't have to be level to still drive decent. I have 1/8" toe-in with newer style sealed tie-rod ends, newer style sealed drag link ends, NOS gears and bearings is a perfectly adjusted steering box, and 4 degree caster wedges ( thick end at back of axle ). I had the exact same set up with 2 degree caster and found the steering way loose, no road feel, and would not track straight. Going from 2 to 4 degrees made a huge improvement, if I could find a 5 degree I would go with it. The only thing that is altered from stock is the lower front end which changed the caster. I have custom made leaf springs with a much softer spring rate to improve the ride so they are softer and set the truck down lower. Caster may mask the problem as Jerry points out, but it's the easy way to fix the problem.
You still need all other adjustments to be right or never will drive right.
