When you get one apart, or if you can research in the parts book might show tooth count so you can do the math.
Being that they didn't offer alternate ratios I'd guess that no other ratios are available even today. Unless perhaps that ring and pinion is borrowed from one of the smaller trucks that did have alternate ratios available, and perhaps they fit or can be made to fit in the double reduction housing.

Some hunting in the parts book might answer some of those questions.
Picture
http://chevy.oldcarmanualproject.com/parts/1929_54/334.htm
Page with ring pinion, section 5.529
http://chevy.oldcarmanualproject.com/parts/1929_54/353.htm

Hard to read that scan but might be 23:8 teeth, or 2.875:1 ratio. In which case, being rather fast for a single ratio rear (if that's the hope for a donor) unlikely you find anything faster that fits, pretty sure nothing faster for GM from that time period.

Last edited by Grigg; 12/14/2016 10:41 PM. Reason: more info
•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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