2. Could be your two speed rear axle is stuck in low. You should be able to get up to 50 or so with out the engine screaming to much.
3. Check for a tag on the transmission, probably right side near the top. My guess is it is a Spicer 5 speed direct drive.
4. Gages will be mostly electronic. Check for blown fuses, a good ground for all your gages. And if that does not fix them get a service manual and follow the instructions.

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-