Of course, you could build that same engine using a Gen III iron block from a 6.0L V-8 (LQ4 or LQ9) with a light overbore. The lower ends are pretty much bullet proof. If you don't want to use EFI, GMPP sells a carbureted intake manifold with an ignition controller. They also use aluminum heads and with LS6 heads with have a CR over 11:1. And you can use the stock lower end.

These engines will twist to 6500 real easy and they even like high lift cams without causing drivability issues. You might want to check these out.