Almost right Derek, OUTSIDE OF THE FACE OF THE YOKES AND OUTER GROOVE OF THE SLIDERS, I changed your picture to show it. Then yes move 1st gear left or right on the mainshaft by sliding it to obtain the 4-7/16" dimension.
When the top cover is in neutral, the 1-2 yoke will be in the center detent, as well as the 3-4 yoke and that dimension should be 4-7/16"
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IMG_2214.jpg (245.71 KB, 150 downloads)
IMG_2217.jpg (198.27 KB, 147 downloads)

Last edited by sstock; 08/07/2019 1:48 PM.
1953 Chevrolet 3100
261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done
In the DITY Gallery
Video of the 261 running

1964 GMC 1000
305 Big Block V6, sm420, the next cab off restoration