F450 vs F350 SRW payload

4x4ord wrote:

Edit: and why is the gvwr limit for both 3500 series and 4500 series set a 14000 lbs?

Simply because of the registration and insurance headaches would impact sales. I'm sure they've considered it, done their sales-projections both ways, and determined the 14k GVWR version would sell more.

As for selling a sub 14k "option" on an otherwise heavier rated truck.. It becomes a little more difficult across this weight-class break, because then they'd have to certify it as a complete vehicle in both weight classes. Doing this at the class 2/3 break is easier because they are already compliant at both classes. But above 14k GVWR, you have two headaches: 1) Greenhouse-gas-limits compliance rather than CAFE and 2) Dyno certification for the motor, which results in a lower advertised numbers even though the output is actually the same. But the lower advertised numbers are sure to confuse some buyers and point them towards the "higher power" class 3 variant, resulting even even more lost sales.