Those numbers are from the first released 4.8/5.3 gen III'S. Still good hp numbers. Ls gives you plenty of options to choose from. The 6.0, 5.3, and 4.8 all share the same block. 4.8 is higher compression ratio because it has flat top piston which makes it great for boost applications. The 6.0 has a larger bore than the others (4.00vs 3.78). In it's early years the lq4 produces around 340hp/360tq No matter which one you choose they all fit in the exact same mounts and everything is the exact same bolt pattern. Either one you go with a good cam and springs is all you would need to push 400hp/tq on the 6.0 n/a.