My gas cap just clicks and slips past the internal stop when i try to remove it.
Tried locking and unlocking but no help.
Anyone have an idea how to remove it - seems i should be able to drill a hole into the cap and inner part and lock the two pieces together with a screw or pin... question is where?

 

The red outer part spins when the cap is locked.

As you suggest, you could just drill a small hole through any area of the front face of the cap, into the main body, then insert a small nail into the hole to unscrew the cap.

You will then want to either repair the hole in the cap body or replace it with a new one.

 

Randy, a 3mm hole drilled on the periphery of the lock inset jams the lock fine, and does not penetrate the inner cap, so there is no ventilation of fumes - cap removed.
Thanks
Neil

 

Try pushing on the cap with most of your weight while unscrewing.

Drilling a hole may put plasctic cap fragments into the gas tank; be careful to grease the drill bit to trap the pieces if you go this route!!!