i just bought my first big block from a co-worker its a '92 454 bored .060 with all machine work done and a few new parts but still has production heads... i ran the casting numbers and it came up as '91 and up, 366/427, closed chamber, genV, 2.06"/1.72" valves. im just looking to build a street/strip motor more on the street side for my '67 c-20 i was wandering if i can get enough power from these heads, i can port and polish them myself to get a little more flow but im not going to do any major reshaping of the ports. so whats your opinion, paper weights or useable?