?? power drum brakes 92 booster 70 master

[fs64]

I have been following multiple power brake threads and went with a 92 booster and a power drum master cyl from a 70 Buick station wagon. The power master cyl piston has a shallow dimple compared to a non powered one but it is slightly deeper than the disc brake master off of the 92. Is this ok?
The second concern is that the ID of the 92 booster opening is = 2 inches and the OD of the 70 master is only = 1.5 inches. They bolt together perfectly and the master cyl flange almost covers the booster recess completely.
Am I good to go or have missed something?

Thank you, Todd