The power stroke is not a Cummins, and they have different operating ranges. The Cummins makes its power and torque much lower than the ford.

Are you stuck with 4.88 gears? Either change to faster ones, or the 0.60 OD, like a 6 speed Allison 1000 from a Duramax could work OK.
The Allison 1000 and 2000 was/is installed behind the Cummins in some medium duty trucks, I don't think they had double overdrive like the GM pickups, but it's just a computer thing, and I hear that can be fixed.

This could be the perfect engine trans combination for you, at an unbelievable price with extra low miles:
http://www.4btswaps.com/forum/showthread.php?t=1670

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-