ok...I measured the shaft on my starter and it is 14 mm.
The color of the starter is black.
No tags to indicate what voltage the starter is.
So the 14mm wins out and tells me it is 6v and the ring gaer has 138 teeth so that too is 6 volt. So even tho the truck has been converted to 12v I do have a matching flywheel ring gear and starter so I think I am good.

I will be changing the ring gear to a new one as it is chewed up in one area.
I will use a 6v one with 138 teeth to keep the match of the stater and flywheel.

Thanks to all who came to my help..........

1953 chevy 1/2 ton with 3 speed 318 on floor and 1955 235 engine