Before you buy, check out the 2015+ models. They did a major interior redesign and it's much better than the prior setup IMO.
2001 6.0: 300HP, 360TQ
2010+ 6.0: 360HP, 380TQ
All gas HDs but the standard cab have the 4.10 standard. You cannot order a different ratio for cas etc or CC gas trucks. Diesel gets 3.73.
I believe the 3500 has a larger rear end...same ratio. 3500 has a different rear spring setup. Everything else is the same. My 6.0 SLE CC has just over 3,000# payload. If you need the extra payload, go for the 3,500 but if you need that much payload, you're pulling a pretty big 5'er and would probably want a diesel. My Uncle has a Denali 2500HD diesel and just under 2,000# payload.
I bought a 2015 6.0 2WD SLE Crew certified w 32k miles for $36k. That was way way less than anything else I saw.
