My '37 has 4 degrees caster due to the ride height front and back. It drove OK with 2, but kinda of loose like yours. 4 is much better. The thickest part of the wedge goes towards the rear. Toe-in should be 1/8" when setting in [ as driven position ], meaning all steering joints loaded. If you are using the original style tie-rod and draglink link ends, be sure they are adjusted up tight and the ball end is still round. Did you adjust the steering box? Is it centered? The steering box has a dead center adjustment that keeps the truck going straight without a lot of input from the driver, this will help keep it in its lane.
There is no reason to change the spring mounting, they can drive as good as anything once you get it set right.
