Good research! Depending on your budget and goals, the 6.0 truck engines seem to give the best bang for buck. They are cast iron block and wiegh about 80 pounds more than the aluminum block motors. The aluminum block motors won't take much of an over bore (max .005 on early models), the iron blocks will take more. The guys that are using power adders are mostly using the iron blocks. Based on your originally stated goals, I would look for a 6.0 either LQ4 or LQ9. But even the 5.3 motors will make good power. One of the car mags built one with an LS6 cam and not much else that was pumping 350+ hp at the wheels I think. Plus they still got good mileage and drivability.

Pat