I use a Gear Vendors hydraulic O/D unit behind a T-5 on a '32 Chevy Confederate sedan and also behind a 700R-4 that is really worked over in a 41 Chevy Master coupe. Both work well and were not a hassle to install. The biggest job for me was to locate the Manual Control switch set in the dash of both. I like the manual down and shift up feature. Instead of 5 forward on the T-5 I now have 10. I'm happy but certainly not cheap but a true worthwhile investment. I bought mine through a Four Wheel Drive shop off Arden way in Sacramento. My mileage improved too.