Rather than an LS7 I'd probably go for an LSX block with CNC ported LS7 heads and after market rotating assembly. You can easily build 454 cubes with this block and make way more of everything in the HP and Torque department for less money.
The LSX block is an GM performance parts iron block that was designed with 2500HP potential
http://www.gmperformanceparts.com/En...166454&engCat=
There's a few shops offering short block and long block options. There'a also a factory crate motor option now for a GMPP LSX 454.
http://www.vetteweb.com/tech/vemp_09...ine/index.html
How does 620 hp and 590 lb-ft of torque grab you?
Unfortunately the 12.5:1 comp means av gas or race fuel only.