The 6.0 and 4L80 combo is an excellent choice. I have both a '02 Silverado and a '03 Sierra sharing that drivetrain. If you're sure about switching frames, I'd check out and see what's available from those that specialize in that area (Morrison, Fatman, TCI etc).

John

~ J Lucas
2006 GMC Envoy 4.2 I6
2023 Ram 2500/Cumins 6.7 I6
2010 Jeep Grand Cherokee (Wife’s)
2002 Silverado 2500 Gas 6.0
1941 Chevy 1/2-Ton
1942 Chevy 1.5-Ton SWB
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