Bill, if you are looking for a modern or different 5 speed overdrive you will find a lot of good info here:
http://www.4btswaps.com/forum/forumdisplay.php?f=22
The discussions are geared to (pun intended) transmissions that work well or easily behind the small Cummins. However, in most cases the same transmissions can be adapted to an ordinary gas engine as well.

Grigg


•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-