try this
http://www.drivetraindirect.com/t_gear_calculator.htm
your tire size is about 40"
With a .8 OD it may work. But getting the military trans to fit a regular 350 may be a problem. Unless you can use the flywheel and adapter from the 409 but I doubt it?.

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-