That is a ratcheting shifter; a factory ratchet. Pushing forward at an angle only allows the next gear. Release the shifter and it pops back to center to repeat the process. It has a factory reverse lock out.
I didn't know it until someone at the track pointed it out. I had already been racing it 10 years or so before I found out.
I really like it; it has several advantages:
a) Stock looking
b) retains the neutral start switch (required by NHRA) and backup lamps
c) I like pushing forward on the shifter, with my back braced against the seat. A lot of guys in fast cars with the reverse pattern shifter complain that the g forces during launch cause them to accidentally pull the shifter back into the next gear prematurely.
d) I added the PRNDL indication from a '73, so I was able to remove the claptrap backfeed rod (which drove the PRNDL in the cluster and locked the shifter with the column) for additional header clearance. No moving parts.
Thank you.... (...I think...)
K