Just finished reading this thread:
All B15 Models 300ZX Calipers on a B15 - B15U.com - Nissan Sentra Forum
People had trouble fitting the 11" disc even when they shaved the caliper almost to the bolt holes/fluid passages.
The Infiniti M30 disc was mentioned as being used by some 240SX guys so I looked it up on the Brembo catalog, it is 273.81mm (10.78 inches) diameter and 22.1mm thick, Part # 225599.
It's only about 1/2 a mm to large in diameter so it may fit with no grinding of the caliper or at most a minimal amount. This would mean you could replace discs without having to machine them each time.
I can't think of a reason to use a B15/Altima disc when you can use a M30 disc