As I understand it, the 4L60E is essentially a fully electronically controlled 700R4. Putting a 700R4 into your '96 will require reprogramming of the computer to account for the non-electronic controls in the 700R4.
4l60e trans that is 2x4 and just replace the rear tailshaft
From what I understand, yes, you simply need to replace the rear tailshaft/tail housing to convert a 2x4 to a 4x4. However (you knew there would be a however, right?), the tailshaft is usually the very last thing removed when disassembling a transmission. This means that you must disassemble the transmission in order to replace the tailshaft. Which is usually what you are trying to avoid when a question like this is asked.