I think they built a little less than 5,000 BN2s and 10,000 BN1s over 50 years ago. Parts are hard to find for the three speed, and it is somewhat fragile, many prefer having a later more robust/more gears/parts easier to source tranny in their BN1. The BN2 bell housing is desirable, and doesn't come up for sale all that often, because most have already been converted to the desired use. I don't know if they sell often enough to establish a market rate. If you don't want it let me know and I will take my chances on doubling my money on E-bay, I know it sounds like a lot for a bit of aluminum, but if that is the direction you want to go I would pounce if I were you.