Since you're going from a 6 to an 8, you won't be able to use your existing trans anyway. You didn't mention if it's a stick or an automatic, but that's kind of a moot point anyhow. The main issue is what transmission you are GOING to use. It's a whole new can of worms on it's own. Until we know that, it's useless to speculate, other than to say you WILL need a new driveshaft.
