What makes a Hurst...

I would say "combining" that it "depends."

My old original Hurst in my '70 sixpack car had a push in/ clip in handle

The aftermarket shiter used a different handle AND bolted / clamped in

The aftermarket shift arms were sloppy on the transmission shifter shafts BUT---

The stockers--which fit tight on the shafts, would not accept the aftermarket shift rods AND used no bushings in the holes.

(I used to cut tiny little pieces of feeler stock to tighten up the shift arms on the aftermarket.)

The conclusion, in this case is that "nothing" interchanges

I finally welded the pistol grip into the original shifter, and used the aftermarket in my 64 426 later on.