[Doug I]

I'd look at it like this ....

1. A Factory Built Car would mean I could walk (although I'd probably take the bus) to a dealer showroom, like what I see, pay some money and drive it home.

2. A Kit would be delivered to someone after which work is needed to assemble and complete the vehicle before it can be driven.

3. A Professional Built Car would be a kit delivered to a person for whom their normal business or specific expertise is to complete that car to a drivable condition.

4. A Custom Built Car would be built from scratch where there were no existing designs for the car.

this helps ?