The 700R4 has been replaced with the 4L60 series transmissions.
The 4L80 is the heavy duty automatic with overdrive. I'd like to replace the Tutbo 400 in my 1-ton with a 4L80 but it cost a pretty penny...
I think if the truck is going to be used like a truck you may want to stick with the existing transmission.
My TH475 has the transmission parking brake stuff on it. If yours does too, then I'd say go ahead and make the swap. Just be prepared to go back the other way if you load the truck and break the transmission...
