F450. The pickup models ONLY come in Crewcab, diesel, DRW (chassis models for commercial may come differently).
Depending on your budget, I'd recommend looking for the 2012-2013, even 2014 model years.
I searched for a year and found the right one (2013) for me at an even 50K, with low miles last fall.
Reason - 18,000lb Jayco Recon ZX 39' Toy hauler.
F450 tow rated (and stops) up to 24,7000 beautifully. A full 33,000 GCVW gives me plenty of margin for Pin weight AND misc cargo in the truck itself.
I knew what I wanted in an RV, so went looking for the right TV to start with.
The Chev 3500 DRW and the Dodge Ram 3500 DRW pretty much in the same class, but I'm a Ford guy.
at 16,500 I think the F350DRW would probably do just as well.