Well I think in 01 GM used lots of the LS6 blocks in the F-bods. The full LS6 motor would be superior due to the better cylinder heads. 98 motors has larger injectors. 98-00 F-bod motors had more lift on the cams. 01-02 motors had tigher LSA. Vette motors are similar.

I'd at least toss in a mild cam if you have the motor in the garage/on a stand.

MPG would be similar if both tuned up equally via EDIT. 6.0 has a larger bore and can support larger intake valves. Most are the low comp variety LQ4 but a high comp LQ9 is a good choice!