If I only put a solid mount instead of replacing factory mounts with the poly, would that wear the factory mounts out quicker or not affect the factory mounts? Is the solid mount an alternative to the poly mounts or is it a supplement to the poly mounts? Also, I got some NGK Iridium plugs and the local auto part store said that they cannot be gapped because the electrode will break, is this true?

 

NO

 

The only problem with the solid mount is gonna be a big increase in vibration in the cab. Gap the plugs

 

If you are only replacing one mount with a solid mount, then yes, the other factory mounts will wear out faster.

Best of luck!