from a pure flow point it goes 2002ls-6 heads, lq-9- 6.0L heads they are similar to the ls-6 but don;t flow quite as well at high liftbot d-port exhaust. then the 4.8L/5.3L heads better flow even w/smaller valves then the 5.7L. lastly the stock 5.7Ls-1 heads. find a shop or one of the sponsor vendors that specializes in ls-1 based motors and get an exhange set of heads. the new heads are very different than previous small-block heads and tinkering by someone who doesn't know the heads can leave you w big aluminum ashtrays. bump the compression shoot for 10.5:1 and a cam no bigger than 212 degrees intake @.050"
and all should be good.

 

So BigTex, between the .050 heads, minor intake and head porting could I have gained 40hp?