Depends on which 8 3/4 you get, and what you're pulling out. Assuming you're pulling a 7 1/4 and if it's a factory A-body rear you're installing, it will fit right on the springs, but, it will have the small pattern, you will need the correct shock plates, and you'll probably have to shorten the driveshaft. If it's a '65-70 B-body rear, you'll need to move the spring perches, and need the shock plates too. The B-body rear will have the 4 1/2" bolt pattern for the wheels. It will also have a wider stance, so, you'll need to figure out which wheel/tire combo you'll be able to use. Just about any other 8 3/4 will be too wide for an A-body without weird custom wheels, offset springs, cutting wheel openings, or narrowing the rear end......or a combination thereof.