Maybe you could try white glue (carpenter's glue) as doesn't stick so well to plastic and can be removed later, but would be enough to secure the guide pin in place.
I have a couple of magnatration 512's that are super loose on the chassis. One's lighted and one's not. The lighted one is the loosest.For the bodies, what kind of bodies are you talking about?
Thin double sided tape on the tabs could help.I have a couple of magnatration 512's that are super loose on the chassis. One's lighted and one's not. The lighted one is the loosest.