1961 3 speed transmission questions

[vetnat]

I am currently rebuilding the transmission in my truck. Needed to replace clutch, and trans would never shift in to 3rd gear (even using levers on transmission to bypass the shift linkages), so decided to look in to it. Have it all apart, can't say I see any reason. Few chipped teeth here and there. Nothing glaringly bad looking. Hoping when it goes back together it will shift in to third.

My real question is about the tail shaft housing. Mine is chipped at the yoke end, so I would like to replace it. But, it looks like I potentially have a passenger car trans? Potentially 5-6-7 chevy? Since I want to replace it anyway, I would like to find a "truck" 3 speed. Are there differences in the gear ratios? If not it doesn't really matter I guess.

To my understanding, the truck 3 speed tail shaft looks like this.