If you've actually got an 8.25 in it, it'll last just fine. I doubt that you do, though; since you said you have small bolt pattern and 8.25s never came in small bolt pattern- you probably have a 7.25.
An A body 8.25 would be a good upgrade, and much cheaper than a 8.75- but as said, they only came in big bolt pattern, in '73 and later A bodies.
Good luck with the Pertronix.