I was not happy with the original BH cranks so after asking here and there and making a couple of failed attempts was finally able to get hold of a well worn set of Zeus cranks. The outer ring is still the original in the drilling fashion of the 70's.
The inner one is a cunningly modified 36 teeth (110 bcd! Necessity is the mother of invention).
By the way, you can also admire the front mech (Have I already mentioned I'm quite fond of it?)