Hey Alan, welcome to BF, and to MTE.
I think you’ll find it much easier to source pivot pins in rod form. 12” is a common length, and you’ll clip or sever off how much you need plus a little, and install them long on each side. Then you’ll grind/file/sand/polish them flush with the bolsters.
Trying to fit an exact pin length seems to me like a recipe for frustration, and an opportunity to wallow out the bolster holes. YMMV.
Parker