I feel stupid even asking but.....
 

Will a 15" rim clear the brakes on my '73 K20? I want to get new wheels/tires and have found some really good deals on 33-35" tires but they are all 15".

i think it all revolves around the backspacing of the rim, more of that if the rim is not deep, it should clear the caliper, but if the rim backspacing is deep, it will most likely work with a little caliper grinding

im not an authority on the 72 axle, but thats usual on the 3/4 ton setups ive seen

i dont see why it wouldnt work.

wont work on a K20 without clearancing the calipers and caliper mount brackets.