The bolt pattern between the 1j/2j & 7M starter motor is the same, however I ran into problems when I tried to use a 7M starter motor on a 2J. It wasn't clearing the ring gear when it was fully disengaged. Neither the ring gear nor the flywheel were standard on my car, so this undoubtably contributed to the problems - just be aware that they are not identical, so if you start swapping in aftermarket parts (like flywheels) you may run into problems with the 7M starter.
The 2J starter motor is also supposed to be a pretty common upgrade for 7M owners, so it wouldn't make much sense to go backwards (if you can avoid/afford it).