to fit it all under the fenders

no,you can not mix the skinny 1 3/4" brake stuff with any of the larger brake parts

the axle off set is diff on the A-body axle

you can swap in some cut resplined large brake axles and run the larger backing plate/shoes/drums in the a-body 8 3/4 housing

or get some custom alxes with the large brake off set and use the large brakes

when you go to large brakes on the A-body 8 3/4,it will make the whole rear axle wider by about a 1/2"...1/4" each side

when I swaped my 68 dart to large brakes, I ran 7" rim with a 4.5 backset - 245/60/15 tire

when I put that A-body 8 3/4 in my 85 truck(bolts right in) I went to 12" rims with the same 4.5" backset and a 29x15x15 M/T(tucks right in the fenders on the truck tubed to the frame rail)

so you have to watch you rim backspace when you swap to large brakes