i found this mach3 postprocessor for mastercam 9 and i converted it to the mastercam x format through the mastercam software which it allows you to do so and here it is:
Mastercam 9 format: http://cnc.novalab.org/files/MACH3B_for_MC9.zip
Mastercam X format is attached
It supports 3 or 4 axis machines!
Hope you find it useful!