Shuttle bus conversion

It would most likely depend on the specific park. Good Sam, like KOA, is made up of many individually owned and run campgrounds; they are not corporate owned, and have many of their own policies and rules and so forth. It might also depend on how the conversion looks; if it's neatly done and looks nice, you'll probably be more likely to have places accept you (maybe despite official policies to the contrary) than if it looks amateurish.

Broadly speaking, the more upscale a park is, the more stringent their requirements are as to what camping rigs are acceptable. Many places really don't care that much provided you're not a safety hazard nor causing trouble for the other guests (or the park management).