Master cylinder for Front disc brakes on 67 Barracuda

Sure you can buy the correct master. Just not from a typical parts store or anyone getting their parts from companies like Cardone.
if you find a used one its almost certainly going to be cheaper than a correct NORS or NOS, even if it needs sleeving.

Check the tables out in the article linked.
Brad goes by "Mastershake" on Mopart. He's made some updates and corrections since it originally came out but still a good starting point.
http://www.moparts.org/Tech/MoparAction/Master_Cylinder.pdf

Other good references are 1967 Shop manual. 1967 parts book.