The cheapest way to change the fronts is with a spindle swap; you can buy aftermarket spindles - that's the best way - or get used ones, but if you get used ones you will have to remove all the shims and you won't be able to get the caster right because the angles are different due to the lower control arms being closer inboard on the later model truck. The cheapest way to change the rears is to change out axles, but good luck finding someone to sell just axles.
What I did was to find a junk '75 1/2 ton and changed out the crossmember and rearend; you have to do a little work, but it all fits good.
