07NBSChevy

Any 6.2 from 2007.5 to 2011 is a direct bolt in. I am not sure on the 2012-2013 engines, should be the same tho. Since yours is 2008, you wont be able to connect the VVT with your existing harness since your truck never had VVT. All 6.2s came with the 6-Speed behind it, you could do that swap as well but would need the harness and ECU from the 6.2 vehicle and some tuning. The 4L60e wont last along after a few full throttle runs.

I have a 4L70E with every Sonnax mod, Transgo Shift kit, Borg Warner Hi-Energy clutches and so on and am still worried about my 5.3 with 450 Hp.