I had the 5.3 before, now I have the newer 6.0 with 6 speed. Overall I love the truck, the advantages are the 2500 series frame and all the goodies that go along with it. The 6.0 tows better, has more power, and has out performed the 5.3 hands down in my experience. Will you be happier with the 6.0? yes especially with the 6 speed. In your case I would opt for the 4:10 if you can locate it. Both engines have proven themselves now for years in relibilty. I have had one 5.3 and two 6.0 trucks thus far and have found the 6.0 to work for me. Yes I have also had both diesel and gas before and for a small block gas engine the 6.0 is no slouch...