I am wanting to start looking for a 4L80e transmission for my 1 Ton Dually. I have a TH400 right now that needs to be gone through. Might as well go up to an extra gear since I'm doing a lot of travelling. Mine is a 454 TBI and the Dana 70hd rear end. I'd like to find a good core but don't know which years will work for my truck. Anyone done it? What does a rebuild cost ballpark?