In my opinion 5.3 lm7 is the way to go. They are cheap ($250- $350), make great power, and give the option of fuel injection. Plus they accept ls1 parts. Look up some of the budget turbo junkyard builds that are making 500-600+ whp on a stock engine and even higher with the addition of a cam. Even if the engine was kept NA, mod for mod you will only be about 15 horsepower shy of what an ls1 would make with similar mods. Anyways thats my 2¢ and its what I'm looking to do with my 72 x :) ...