I know your pain as I have an Ofmega Mistral crankset coming in soon in the mail for one of my projects. I'm already stressing about not really knowing what BB/spindle to use on it. I did see in some internet threads that some later Ofmega cranks might have standard spindle tapers and its most likely just the older Ofmega cranks (early 80's and earlier) that required the Ofmega tapered spindles.
I just hope it will be OK when I test fit it on one of my ISO tapered spindles on my other bikes.

Chombi