I don't have a P13 or D24, but do have a Mopar flathead 6 in my '56 pickup.
Like a lot of folks, I feel a need to drive faster but run the engine slower.
I am working on getting the clutch housing that uses a hydraulic slave cylinder to go with the hanging pedal setup that I plan on installing. These housings have a larger trans mounting area than the stock one so I have lots of room to drill new bolt holes.
The overdrive I am currently planning to install is a New Process A833 from a late 70s Mopar. They were used in pickups, vans and cars. I want to use a floor shift so the stock overdrives are pretty much eliminated because of the shifter issue. Nobody makes a floor shift for the old selector shift mechanisms that Chryco used, along with Buick, Olds and a few others. So I considered other overdrives, Saginaw electric on a full sychro trans and a T5 among others.
Has anyone tried the 833? any feedback? It looks to be a fairly easy install, other than the parking brake issue. Am I missing anything?