Do find out what the high side ratio is in the rear, and then use this site for calculating speeds. http://www.drivetraindirect.com/t_gear_calculator.htm

If you know what rear you have you can find out what faster gears are available, and if that's all you need to go as fast as you want.

Why don't you want the two speed? Most (if not all) two speed rear axles share a housing with a single speed model, so a single speed center section probably fits in place of your two speed if that's what you want.

You may still need an OD to go as fast as you want, but lets do this one step at a time.

What engine do you have, and does it have a completely round flywheel housing that the transmission bolts to with 12 bolts? or not?

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-