I kinda made a statement in my post above about 2-rail and 3-rail trucks (not wheels).
Is there a difference between the trucks themselves? Should I be able to simply swap wheels sets or is there more to it than that? I was having issues with some trucks and not with others, but I couldn't begin to tell you all the brands of trucks I have.
Wheels, or at least axles, can be different too. Some have pointy ends and some are blunt and many times the blunt axles won't fit into certain trucks.