what Bore master cylinder

Doesnt sound like you are staying stock look,so if I were you I would go to the light weight Mopar Alum mc.
This is the one I installed on my 65. You will need the 2 to 4 adapter for it.
This one is a 1 1/32" bore. Stops real nice. Got a new mc with adapter for $100.00.
Also used the stock push rod with it. Simple bolt on install.