Yes, the master from a '73-'75 A-body POWER disc brake car has a 15/16" bore and a groove for the manual brake push rod retainer. Of course the retainer is not included. You must buy it from someone like me or Greg Z.

What are you running for front calipers and rear wheel cylinders? Stock parts should work fine with a 1 1/32" bore master. Maybe you actually have a 1 1/8" bore unit.