I have a 69 Saginaw from a C-10 truck. I had to make custom everything for it to work but it's a great transmission. I had a non syncro 318 which I pulled. I set the 318 on the curb, and literally gave it to the first person that drove by.
I made dies at work to stamp the holes in the shift arms after determining the correct length. A double bell crack was developed to still use the column shift.
The blue background pic is a mock up that shows the layout.
Also, my Muncie 318 and Saginaw were there same length. Around 21.250".
Saginaw 3 and 4 speeds did not have a short tail shaft option like the 58-64 Muncies.