I think David (Carolina.....) may be able to help there. He's posted before on rebuilding his booster. You might check Cardone for a rebuilt or even R&R. I got mine form Cardone, but although it seems to be good, they didn't even paint the thing, just bare metal.
Many of the so-called replacement boosters sold do NOT fit our cars. The 8" Bendix for sure will not fit with the shock tower supports. Ask me how I know!
When I did my booster add-on ( I did not have PB before), I first tried the Bendix, but quickly found why it would not work. Also at that time, my steering column was out because of the need to rework and drill the 3/8" bolt holes. It's a lot easier with the column out, seat as well. At least you'll need to drop the column as your just doing a replacement.