This forum is great for the B series Cummins, both 4 and 6 cylinder.
http://www.4btswaps.com/forum/index.php
Seems most people left the Yahoo group and went to the real forum.

You should seriously think about an overdrive transmission, as the Cummins is a relatively slow speed engine. For best economy you want to run down the highway at 1,700 to 1,800 rpm. Use this site to help figure gear ratios.
http://www.drivetraindirect.com/t_gear_calculator.htm

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-