A heads up on the tailswap swap, the entire trans has to be taken apart to get to it. an you will need a speed sensor and reluctor gear. i did this to my 4L80E as it came from a 4x4 silverado.
it MAY be different on yours i dont know, but here is a good source of info on it
http://www.ls1tech.com/forums/automa...-4x2-help.html
and
http://www.transmissionpartsusa.com/ was the only place i found that sold the reluctor gear individually. just DO NOT buy your rebuild kit their. they screwed me on that. (sent the wrong one (a cheaper kit for the 91-96 trans) and wouldnt take the item back because i opened it. which i understand IF it were the right damn part.) and i ended up getting the kit locally for over $110 cheaper. but hope this helps!!