I had the 1" initially on my T-Bucket, then changed the pedal ratio, and then went to the 7/8". The car has 11" disks up front and drums on the rear so there is plenty of stopping power. These changes all reduced the pedal effort as well as finally 'softening' the pedal for an overall nice feel and effort. I always warn those that want to drive the car that these are not power brakes so be ready - most folks have no experience with manual brakes or don't remember what they were like years ago - expect that just resting your foot on the pedal like they do in their daily driver is enough to stop the car.
However, the proper deteriming factor is the disk caliper volumes you'll be running front and rear and how those match up to what the master will provide. I believe that once you verify the volume requirements, then you can address the bore size.