First, What is your intended use for the vehicle? If it is just a driver with no heavy loads the 700R4/4L60 is the least expensive swap. If you are carrying heavy loads of towing heavy loads frequently the the 4L80E is the transmission you need.
The 700R4 only requires a lock up kit to control converter lock up, a rear transmission mount relocation and the driveshaft will have to be shortened. As well as the transmission and converter of your choice. If you carry or tow heavy loads you will have to use 3rd gear only no overdrive.
The 4L80E requires a computer to operate, a TPS sensor for the computer if column shift the frame mount has to be relocated rearward. Cooler line relocation. Transmission mount moved rearward. Driveshaft shortened and a Mechanical speedometer conversion if you have cruise control or wish to continue to use the original speedometer.
Here is a 4L80E swap in a similar vehicle.
http://67-72chevytrucks.com/vboard/s...YS+Performance