Alright I've been looking around a lot on the internet today and i have come to find out that I would prefer to use the 6.2 instead of the 6.5 because its naturally aspirated and will directly bolt onto my 4L60e, however the 6.2 it totally mechanical and so I would still need some kind of transmission controller.
Differences between gas & diesel 700r4's [Archive] - Diesel Place : Chevrolet and GMC Diesel Truck Forums
I read this and it seems to have mixed opinions.. I just had a reality check. There is no way I could afford the Isuzu swap at this point however something that is direct bolt on and that all I would have to jack with is the electronics of the transmission shift points ect, Seems much more do-able. Even if it wasn't meant for the 4L60e the 700r4 isn't that different. So it truly does seem much more simple and a lot more practical than swapping in an Isuzu.