I've got an 89 TPI 350 with 150,000 miles on the original engine with very minor mods which include a 3 inch exhaust cat back system, air foil, new plugs & wires, K&N air filter, TCI rebuilt racing auto tranny, and a few free mods here and there. The car runs great and has never failed me (knock on wood). I wanted to add some more HORSE POWER without getting too crazy as I don't race often, but still do it sometimes. Was wondering if it's safe to assume a 100 shot wouldn't tear things up in my broken in engine?

 

I would acually start off with some headders. As for the Nitro, it all depends on how you drive the car, and how much you use the Nitro. On an engine with than many miles, I would be weary of using it, but thats up to you.
Good luck!