One of you was wondering when the overdrive option disappeared. About 20 years ago, I bought a non running 66 Impala won with a 283/195 horse engine. It was a three speed, but a partially disassembled Saginaw 3 speed with the overdrive solenoid and some wiring was in the rear seat well. Also, the overdrive handle with the cable was still mounted on the bottom of the dash, and the OD switch was still on the carburetor. The car had a 12 bolt with 3.73 gears in it, no posi. I sold the car to someone else who wanted to race a Stock Eliminator class with it, he probably still has it,I haven't seen him in years. That's the latest overdrive app I ever heard of.