Have you seen this? If you have the $$, you can go to a GM facility in Michigan and assemble your own LS7 or LS9. CHEVROLET PERFORMANCE OFFERS BUILD YOUR OWN LS7 OR LS9 CRATE ENGINE PROGRAM : The Official Website of the Super Chevy Show

You might also consider an LS3, you know how low Corvettes sit and with that pan you may get your 57 as low as you want with out the hassle of plumbing up the dry sump. LS3 is is 6.2 liter with 430 Hp or you can opt for the hot cam version and get a little more HP all for about $7k and that comes with a GM warranty. That's 1/2 the price of the LS7.

Pat