The '87 custom deluxe brake booster did end up fitting on my '63 firewall with no modification, the bolts lined up with the bolt holes for the master cylinder, and it fit through the hole in the firewall which was where I thought the issue would be. However, it is wider and longer than the old brake booster. It fits fine with my stock 230, but those with aftermarket intakes, or possibly v8's might have clearance issues, I'm not sure.
Taking Captainfabs advice, I found a late '70's C10 master cylinder at a local autoparts store, which fit the old (but still working) brake booster. I cleaned up the old brake booster and painted it making it look brand new.
I'll be giving my father the '87 master cylinder and brake booster for his '87 custom deluxe. Since he's helped me so much with my current project it's the least I can do. His truck doesn't stop for crap anyway, so I'm sure it can't hurt.
