I'm very sorry to be so confused after @gunrunnerjohn gave me some great help, but I don't think the Lionel stuff is the same. I've attached pics of the Lionel speeder body and wheel set. There is no screw on the Lionel body that I can see like the one on the Kline. On the car body, the wheels set in slots that are circled in red. Those slots, and the entire body are metal. Each wheel assembly has 2 square metal holders/bolts (?), circled in red, that fit securely into the slots in the body (note that the holder in the picture isn't in the right spot). Those holders are not electrical conductors, they isolate the body from the outsider track rails. When I test the continuity from the wheels to frame, I get nothing. GRJ said to use the screws that secure the motor to the body as ground. Those 2 holders are circled in blue, and that's what I plan to do. I'm waiting for parts to finish this, so I can't check anything out right now. I'll post something when I do, perhaps late next week.
I made the post in order to see what the OP, @davido1224, found out in his experience with the Lionel speeder.
I do appreciate the suggestions.