The guy was asking "what do you guys run on your second series pickups.." I think we all know he is talking to owners of Chevy or GMC trucks built about Mar 1955 thru 1959. He has a 1956 Truck with the new design that runs from 55.2-59, that share the same basic Chassis and body for which he needs tires, except he lost the chassis. If you want to correct him, but you don't want/can't answer his question, knock yourself out. Yes, there are differences in engine options. Chevy had option changes also. That's not way too many differences. Positive 6V ground or not. You can call 55.2 and 56 the same truck as you can 56 and 57 and so on.