This is a Tremec mid shifter adapter. They must be expensive. We were going to use it in the billet chassis car but it was too big and we didn't like it. We billeted our own for that car. (See page 158 of my book here
http://www.kirkhammotorsports.com/book_aoe/aoe_14.pdf )
We took the bearing out of the shifter and used it on the billet chassis car. You will need to find a new bearing. You can probably get one pretty cheap from Standard Transmission. Nice guys. Notice the prototype short shifter for the billet chassis car as well.
$25 takes it.
SOLD