904 abuse

Hey gents. I was wondering just how much abuse a 904 can take. A couple of years back a good friend sold me his 904 for $50. It has about 2000 miles on a rebuild, manual valve body, shift kit, deep pan. He ran it behind a blown 340. Dont know how much power he made, but he sold me the tranny because he said it was slipping a lot.

Would it make sense to rebuild it, or my spare 904, with heavy duty parts. I plan on building a 318 on nitrous and racing my Barracuda weekly at the track as well as driving it on the street.