Your engine already has a lot of good parts in it. All forged internals and big port heads. If you already have the single plane intake and Holley 800 carb, I would rebuild to stock except for a hyd. roller cam like the Crane 139011. It has 226 int./234 ex. duration @ .050. .587 int./ .610 ex. lift . And I would send your heads to Jim Valako, Jim V here on the board for his wedges and port work. While they are there he can do a valve job and set up the springs correctly. Real tube headers would be better than the stock exhaust also. I bet that would make over 500 hp and still be drivable.