I would just put on a shift knob that will thread down enough to hold down the "cable" so the shifter can always move. Does that make sense? Never had a problem with it going out of gear.
I made the guts to fit in the bearing section of a skateboard wheel, and it is mounted on a Lokar shifter (T400)... Lathed down a center slider, and threaded an outside section and made it fit with old bearing casings... Center "button" unlocks the trans lock... Adjustable with a lock nut, so you can get it to lock/unlock at the correct distance...
I thought about finding an undrilled dice and drilling so the button ended up in the middle dot . I have a knight head that was a liquor decantor that I'd like to use though.
I really dont' know if this will help you but: Back a bunch of years ago, I made a tall shifter for an OT custom car, and used a stock GM shifter. It had a plastic rod in the center of the hollow shifter stem. I made up a long stainless tube for the stem, welded a stainless bolt to the top, with a hole drilled out in the center of it. I bought some nylon rod, and cut it to length to take the place of the short original lockout rod. For a shift knob, I got a large dice, and drilled it out, tapped it to fit the bolt, & made a button to stick out the top, to actuate the lock out. Worked very well. You might try the same approach to your shifter???? I never used one of the Lokars, but it must operate similarly.
When I ordered my Lokar I had a 8 ball put on it. God knows I stole enough of them from the pool room to use on my shifters in the 50's.
First time around I ordered LoKar's 8-ball, painted it white and foiled the button. Next I candy-coated the "iris" (button) blue with a black pupil, and added a highlight dot and coloured "flecks". Finally I added veins and arteries to the ball ..and, voila! Eyeball! I've since added their adapter and a nail-polish painted resin Fink. -Dave
Nothing special and a little blurry, but I made this knob from a red plastic ball from a 60's/70's driftwood centerpiece. Still has the Lokar button. Blue
I think American Shifter is a 3/8-16, but couldn't tell you for sure. We have the adaptors and shit-tons customs knobs. The majority are high-quality USA made. Just click on our link below if we can help you.