I used to work at a car/truck spring warehouse in Michigan that supplied nearly all of the springs for JC Whitney. The first thing that came to mind was JC Whitney, but the mention for LMC is also a good idea.
If you live near a larger city you can check with the local spring shop. Hopefully you have the model with leaf sprigs, as some of the '72 models still used coil springs. I have a '72 half ton and when I replaced the rear leaf springs I chose the set with an extra leaf in them, just guessing I think the part number is 22-545. (wow, guess I filled too many orders to still know the part number) If the local shop is big enough they may stock the spring, or, you can ask them to add leafs to your springs or a new set to give you an extra inch or two in height. Remember though, one or two leafs is a good thing, too many is not good and feesl like you have a block of steel for suspension. JC Whitney, LMC or the local shop should all have new rubber bushings and anything else you need. YOur truck should have a sway bar (or anti-sway bar) on the front, perhaps it just needs new bushings? I haven't found a need for one on the rear, unless you have a camper mounted in the bed.
Hope this helps.
