* C10: Refers to the *model* of the truck. It's a general designation, and a C10 could have either a Fleetside (or "standard") bed or a Stepside bed. The C10 simply indicates the size and general features of the truck's chassis and cab.
* Stepside: Refers specifically to the *style* of the truck bed. A Stepside bed has a noticeable outward step or flare in the side of the bed, giving it a wider appearance. This was considered a more stylish option compared to the simpler Fleetside bed.
In short, all 1963 Chevy Stepsides were C10s, but not all 1963 Chevy C10s were Stepsides. A 1963 C10 could have either a Stepside or a Fleetside bed.
