The grip frame will fit,,, but remember the trigger return spring is different. It's an easy modification with the addition of a custom piece inserted to put the OM return spring & plunger in though. I've done several that way.
Yes as long as the NM grips came from a Mew Model SBH with 7 1/2" barrel or longer. NM SBHs with 5 1/2" barrels or less have smaller grip frames and grips.
thats correct, the round trigger guard loops are shorted, smaller, akin to the 'reds'............
if the grip frame has the 'square back, ( dragoon style) then they can and will interchange, its the medallions , and hardware (escutcheons) that make the difference as to vintage,,,have swapped the parts around in a pinch to repair or fix an "old pair" or even a single broken ,damaged panel,,,,save them ALL........