Are the SAM systems interchangeable between model or does each game have unique boards? Take for instance a Spider-Man and Iron Man, what boards, if any, would be interchangeable between those two systems?

I was originally planning to go with some early SS pins from the 80s, but the pricing is just ridiculous for what people are asking for them and most need work. I just can't justify these prices as much as I like the machines. I decided to go with the SAM system games since they seem to be fairly reliable.

I would like to pick up some boards to put on the shelf in the event Stern stops producing replacement boards since these are over a decade old now. What components would you recommend shelving?

Thanks

Chris