Disc brake pedal ratio different from Drum brakes?

Order a 73-75 A-body POWER brake 7/8" bore MC but run it manually. I guarantee you will like it. Less effort than a 1-3/32.

I have tried 1-1/8, 1-32 and 7/8 in my 68 cuda with manual 73-75 discs. The 7/8 bore is the way to go for most people.
I think the 87diplomat master cyl is a small bore.