How far do you plan on taking the truck? What kind of supercharger, do you plan to tow, and will the truck be driven/commuted daily? I would honestly look at doing a 4L80E swap if you want to be around 600whp-700whp area as even a built 4L65E from any of the aforementioned trans shops may have trouble running that much power in such a heavy truck.
Unfortunately I do not have info on the tcase input shaft compatibility with your transfer case to the 4L80 which may cost you $300-$400 but you can find a low mile 4L80E for about $1000, add a shift kit, 3000 rpm stall billet converter, big trans cooler, and you'll have a bomb-proof transmission.
Depending on the supercharger you might even be happy with a stock converter but it all depends on what you want out of the truck. I think you'd be quite happy with a fully built FLT, RPM, or Performabuilt 4L65E if you plan to keep the power around 500-550whp. The torque converter is completely dependent upon which cam and supercharger you plan to use. Give you decision quite a bit of thought if you prefer not to buy things 2 or 3 times.
