stock 500 hps carb motors,gil exhaust ,,,refreshing stock heads w/ port work, cut .20 or.30 thousands ,,5 angle valve job, and bigger cam like maybe a 525 cam. what can i expect to gain in HP.

Thanks

It depends a lot on the porting work. Probably 40-60hp.

Hp 500 with stock heads and a 525 cam on a 2007 dyno made 532 to 536. We have dynoed 5 of these all made about the same. Head work will made more . As for a cam I would call Bob Madara (585-654-8583) and have him make you a new cam.