I didn't realize that the BB had the 26 tpi as well. Even though the threads are different it is serviced the same way correct? Would the bearing cups be compatible with a replacement tapered axle so I could put new cranks on it? I would prefer not to have to find a cottered crank of the right size.

Did Raleigh use a different chain size?

I suppose I can re-tap any eyelets or use through bolts if I can not find bolts with the right thread count.

I am not too worried about the zippyness of the hub. I have ridden a nexus 3 speed for a long time and was happy with it. Even if it is a bit slower I would rather have that than a derailleur on my go to work bike.