Hmmm... not really what I wanted to hear, CJ :P
I found comfort thinking that the 744 was one of those rare aircraft on which you did know which FMC was the Master.
The Navigation displays are independent (wrt FMC map data), but in matters of thrust control, I believe there are interlocks (e.g. you can't arm the autothrottle if the FMC L/R switch disagrees with Master FMC relay).
Cheers.
NSEU