six Trans

Don't know if this will answer your question or not, but I have an OD833 4 speed in my 66 Valiant. The transmission and bellhousing came out of a '76 Volare and bolted right in after I found a '66 4 speed floor hump. All I had to do to the driveshaft was change the front yoke. The transmission is a Chrysler 833 4 speed that is basically a 3 speed with an overdrive 4th gear. These came in '76 A bodies, '76 up F bodies (Volare, Aspen), and half ton pickups and vans. The F body unit is more desirable since the shifter mount is in the same place as the A body and the tailhousing is the same length. The truck unit can be used, but you will have to make a shifter mount for it and have your driveshaft shortened since the truck tailshaft is longer.
Now I can cruise at 70 no problem, where before with the stock 3 speed, 50 to 55 was about it. Don't know how it happened, but the Valiant has a 3.55 rear gear from the factory and the slant is much happier with the OD 4th gear. My gas mileage is around 25 MPG. Hope this helps.