That is kind of to the point I have been making.You can't/should not just pick out one part(the heads)of a combo.People do that all the time and the question should be larger than just that.If he wanted just L31 96 to 2000 results,then he should buy that,Vortec heads and all and rebuild it.Engines are a system and just one pc of it is not sufficient.Compression ratios.cam.well you know what I mean.I