For the money involved, and the power produced, I say there is no better engine than the LS series. Its common to find a 5.3 out of a pickup / suv for $350 or less. Search craigslist if you don't believe me. Put a car intake on it, switch the cam, and viola, 400 rwhp. Cam only f-bodies have been making 400rwhp for years. The record for a heads / cam ls1 is well north of 550. You must also take into account the parasitic solid rear axle.
On a side note, I just bought a '78 280z with a SBC/th350. Picking it up this weekend. I'm torn as to what direction to go with it. Cheap, old school, learn about carbs. Or, keep me in my element with an LS engine. But they are more expensive to modify.
Sorry for the pseudo thread jack