...there were a couple of generations of Ofmega cranks and spindles. The later ones used a size and taper that was more or less standard.

The earlier, smaller ones are quite unmistakable, and if yours fits on a spindle with similar measurements to a standard Campy, you should be OK with just about anything as long as you allow for the differences in how a JIS spindle will affect your crank position and chainline/Q factor.