The main reason I wanted to use the Holley heads are because I got them REALLY cheap from a friend. They worked pretty good for him, but he also had the stock 302. MM and FF also tested them and they made good numbers, which I realize was on a 302 and I also take those articles with a grain of salt. I also bought the Trick Flow cam and intake for $200 total from a friend. I plan on giving the cam to my dad, I want to go with a FTI one. The parts may not be the best I could possibly use for the 331, but I think I would be able to get away with using them and be happy and upgrade as time and money permit. I want this engine to last me a LONG time and I plan on keeping the car a long time.
FWIW, I worked with a kid who has a 89 GT vert with a 347 with Trick Flow Street heads, intake, and STOCK cam. He is in the low 12's. I don't remember exact times, but I went down to the track once with him and saw it myself.