In the same photo album are pictures of the shifter tower, GM made I think. Looks like top of an SM420 and shifter stick may be interchangeable.
Spicer also made a more compact shifter, could be bolted to side of main transmission or to the frame/bracket on frame.
Linkage is just 2 rods and appropriate clevis ends.

•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
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-