My kid has a newer curb-find mountain bike, Walmart brand Roadmaster or something...

We thought it might be fun to find an old cruiser frame to paint up and put the new parts on. Nothing fancy, something inexpensive. Looking for something that would have threadings compatible with newer parts. I'm not familiar with these bikes and am not sure where to start, Schwinn, Murray, Huffy, Sears? We have a local bicycle swap meet coming up and it would be nice to score something there.

Thanks.