For stopping a load of that size you need to depend on the trailer brakes and not on the trucks brakes. Besides the F250 and F350 use the same brakes unless you have a F350 dully. For the going better, that can just be a issue of gears. Did the 250 have 3:55's or 4:10's, same question about the 350, other than that they are the same or 99% the same. Also if you look at the spring packs in the rear you will find that they are the same, the 350 may have a helper spring installed but that would be about it. Now I am talking about the single wheel 350, if it is duly then they will be different.