I will never put a factory a body 8 3/4 in an a body for many reasons. Very expensive and thinner housing tubes.
A better and much cheaper alternative is a 8 3/4 from a 1966-67 b body like a coronet or satellite. For around 150-200 bucks you get a stronger housing, better brake options, and large bolt pattern all in one shot. Only small drawback is its only an 1 1/8 wider per side. Hardly noticeable really. Tons of them are available. Just my 2 cents. P.S. Make sure you get the shock plates too.
