I have had BW OD behind Ford Y-Blocks for 50 years. Years ago I had them wired so I could shift into OD in all 3 gears. But I admit that I was silly when I was younger. I even had the reverse lockout removed so I could use overdrive in reverse. Going 30 MPH backwards is just plain stupid. When I got serious about driving, like proving who had the fastest car in town, I locked it out of OD. Shifting the Hurst Mystery shifter was so much faster than waiting for the OD to shift. And this silliness came with a price. I knocked out an input shaft and cluster gear about once a month. This left me with just second and hi which was no problem with a 3.89 or 4.11 rear. But I had to remember to park where I didn't have to back out of because knocking out the cluster gear took reverse with it. With all the front sections I tore up, I never remember tearing up the OD unit itself.
For normal driving I kept the kickdown switch under the foot pedal where Ford put it. I think Chev has it in the carburetor. To shift into OD, I just floored the pedal. To shift into OD, I merely let off the gas until I felt it grab OD and then floored it again.
Hurst made a Mystery Shifter especially for OD transmissions. It is a modification of a regular shifter that allows room for the shift solenoid. I see NOS Hurst shifters for Ford T85, T86 and T89 OD transmissions, but I'm not sure I have seen one for a Chev with OD. But I really never looked either. I recently bought a 68 Saginaw OD that I want to put in a GMC. I am thinking of using a shifter for an auxiliary transmission.
