If by "stock Shifter Bushing" one means the forward round two piece bushing and /or rear wrap around bushing that holds the rear of the shifter near the floor, they do not harm shift quality. They do a great job of isolating harmonics, much better than harder flashy polyurethane. The OEM front is hard plastic and does as good a job locating the shifter in relation to the trans as poly. The rear bushing just holds the rear of the shifter up near the floor away from the driveshaft while allowing unfettered rotation of the shifter with the transmission as the drive train reacts to torque applications.
The shifter itself, whether OEM or AM, simply pivots in a ball socket, it's throw is a function of length above and below the ball .... "ratio" in other words, as the transmission shift linkage inside and as transmitted via "spool" defines the positions and gates.
I have a
Hurst Billet Comp+ shifter now, I did the original install, I have extended the handle several ways looking for my favorite spot, ....
..... but the first thing I did after initial install was to drive it and notice the noise / vibrations.
I removed the Hurst, pulled the red poly bushings
out, installed the
OEM front hard plastic bushing and cut the center out of the
OEM rubber rear bushing with a long skinny blade and it then fit the rear Hurst's rear tang perfectly, and it has some ribs on top so it doesn't transmit vibrations to the floor.
No noise and vibrations now.
I strongly suspect that the same result would have been noted with just changing the rear OEM rubber in place of the poly.