I wish someone here that has a Topline cranset already on their bike would chime in to help you out, and I am curious too on what is the final word on the required BB spec for it....but as you might already know, these cranks aren't so common out there.
One other note I have for you is that what ever pedals you end up using on these, you will need to make sure that they have flats on the pedal axle to install and remove them with a wrench, as the pedal threaded holes do not go through the crank arm like they typically do on most cranksets, so there will be no access to the usual allen head wrench hole you see on most newer pedal sets, to tighten and remove the pedals from the crank arms. I've seen Toplines with their pedal holes drilled through, by their owners to make it possible to use pedals without the flats on their axles, but I would not suggest doing so as there is not that much material on the ends of the crank arms (for lightness) and you might structurally compromise the crankset if you do so....