Quadra-Drive Vari-Lok mod?
 

Doing some searching on these critters.
Seems someone made a reference that you could block off a check valve and they will do a positive lock up, much better than the limited lok stock.
I found this site with pictures of the thing.
http://www.rallyanarchy.com/phorum/r...5,12323,page=1
Then other sites referenced this mod but no detailed write ups.

So what does the collective know?
Has to do with this.
Also guy mentions shaving .080 off it to get it to fit in an XJ housing.

https://i140.photobucket.com/albums/...k/IMG_1038.jpg

Did you try the modification?