I was looking into it. You would need a shaft driven Reverse box to keep reverse. There are a few mostly used in street bike kit cars in europe I think. It would be 2wd only. I was thinking a small Samurai transfer case would work to keep 4wd. They had some that were divorced from the tranny, so they would be easy to hook up. Not sure if theres enough room for a F-N-R box and a transfer case before the rear diff though.
Yeah, use the stock diff. I would atleast. Are you doing the 1300 or 1800?