Gas Cap/filler Neck

I put an MTS 1978-86 CJ tear gas tank in my 67 and am having a hard time finding a locking gas cal to work with the filler neck. The bottom of the cap hits the edge of the fill hole in the filler neck. I am wondering if the hole used to be centered and the repro filler is off center. Does anyone have a picture of the inside of their original filler neck showing whether the hole is centered?

New filler neck. The silver mark near the rivet kf the hole is where the gas cap hits it.

New gas cap. The black mark near what I think is the vent hold is where the cal hits the filler neck. There are two marks because I rotated the cap 180 degrees to see if that made a difference.

 

Fine tune it with a hammer? It was most likely not position in the fill neck correctly.

 

Knock out the unleaded only dohicky and it will fit perfectly. No smog check needed for that year of car so no problems removing it.

 

I tried two different caps that are intended for that year filler. I tried each several ways with and without the key, so I am pretty confidently I put them in properly. Neither fit properly. Is the unleaded only dohickey the white plastic part in the middle? I like the idea of addition by subtraction.
MotoRad # MGC792 (vented)
MotoRad # MGC234KA (Emission control venting)

 

No. It’s the small offset hole in the filler neck that was put in to stop you from filling up with regular gas when it was available. Kind of like e85 and unleaded and diesel all have different size neck openings

 

Understand the locking cap fits many makes and models, not just your application.
I would take the filler neck to the parts store and try several till one fits.

 

Epilogue: Here is the summary of what I have learned from you guys and trying different caps.

These following caps do not fit:
MotoRad # MGC792 (vented, locking)
MotoRad # MGC234KA (Emission control venting, locking)

This cap fits:
MotoRad # MGC811 (vented, non locking)

The other option would be to Dremel out the restrictor in the filler neck that is in place to ensure that you are only using unleaded gas. This would cause a problem if your car needs to be emission tested but should not cause a problem for older cars like mine.

I’m decided to roll with the 811 until I get siphoned and then consider making a change.

 

You can get a wire mesh for the filler tube to deter a siphon.