Opinions will differ from what year may be the best. "If it's a FORD, it's all good". IMO, I would say the 78/79 models F250s were better because of the upgraded power steering from the Power Assist. Asside from 77.5, the Front ends were open knucked. Also, if it matters, the In Cab fuel tank moved back to the rear, so you could change the 19 gal out to a 38 gal if you wanted.

But, no year is really that superior to the next. Just depends on what you like the best.