A body 8 3/4 or B body 8 3/4 ?

Going from A body rear brakes to B body axle standoff/drums does increase the overall width of the axle. It increases the width about 3/8" per side or 3/4" in total.

The 66-67 rears are the best to find for the swap if possible. The perches are 44" on center instead of 43" so a little pull on the spring and it goes in. Done it many times. It's better to move the perch, but, sometimes you just don't have the resources.

Yeah that chart is a POS! :)