Don't limit yourself just yet with so many details that can be worked around. Input shaft spline count for example is of little importance because clutch disc is easy and cheap to swap as needed.
How about ask for and come up with a list of OD transmissions that would be a reasonable fit behind the 292. Then after understanding the choices weed that list down to the one you like best for whichever reasons suit you.

A GM NV4500 five speed OD would be one reasonable choice and worth researching.

•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-