Actually, you do exactly what the automakers were doing back then. In my 1959 Ford Shop Manual there are drawings of 4 chassis, one for the convertible and hardtops with an X in the center, one for the sedans that does not need the reinforcement, one for the retractable and for the wagons and Ranchero. They all have the same front clip and wheelbase, but the center and rear sections are slightly different depending on what type of body sits on them. That is the kind of attention to details that will make your models apart. I like what you do a lot.
Cami