I have one just like it.. when you find out we will both know.
I replaced mine, it has the same welded shifter mount and knob locknut..... see if there is a PN on the other side. I searched the PN I have on the side and no joy. I think its the plate PN.
I think this shifter came of off a Muncie tranny, at least this one did.....IDK where the PO got all the parts he thew in the car....
I think the welded on style shifters are the "old" style , which was replaced with the bolt on type possibly around 68.
I also THINK your shifter ( and mine) has a new PN of 3916848. The competition plus shifters seem to be the same shifter with different shifter handles.
I chose PN 391848, which simply has an offset ( to the right) handle 3916848.
The shifter you have I think is a over the counter shifter. The number on it is the serial number,not part number. I think all Hurst factory shifters did not have the 3/8 stop bolts on the front,and back. Factory shifters had a 4 digit number on the shifter body, and 4 digit numbers on the levers.