You're exactly right, Paul. My '02 2500 D'max 4x4 CC, 6.5' bed had less payload than 150/1500s from about 2015, and onward. I towed my old FW, 11,360 GVW, and was about 1,000 over on my combined GW and 600 over on my rear axle, but with 265 tires instead of the OEM 245s, I was =under= by about 800 lbs on the 265 tire rating.
Yeah, a gasser F250 would handle a 12k GVW FW OK, but a 350 would handle it great, not just OK. They're the same truck, with a bigger spring package and, maybe, brakes (can't remember). Biggest cost might be in the registration difference, depending on your state. :-)
I'm like you, in that I don't want to go much bigger than what I currently have, but I also have a 30' GN trailer and had to think about that, as well. Any future FW upgrade likely won't be more than 13k GVW, from what I'm looking at now, so I =could= have stuck with a 2500, but the price differential just didn't make sense to go with the 2500.
Lyle
