An 8 3/4 will live, but I'd opt for a Dana personally that way you wouldn't have to worry about breaking it. We ran a 29.5x11.5 on the mini tub duster. I run 31x14 on my back half ladder bar car, but could go alot wider if needed. As long as the rear frame rails are good a mini tub would be okay for what your trying to do. Putting a BB in an A body and easy to work on is not simplest. We have the inner fenders removed on my car and snout bars going from the cage to the frame tying in the shock tower. Run TTI headers, they fit nice, but is nice in some spots. Before we caged it we ran fenderwell headers and they were SO much easier to work with but limited you on the front tire size. As far as weight my 2 dusters are

1975 back half ladder bar, dana 60 440 with alum heads, intake, full cage, only fiberglass is bumpers - 2950 lbs
1973 mini tubed dana 60 360 alum heads, all steel - 3040lbs

both cars retain factory dash, interior panels and have carpet on the floor.