I have an early 70s Raleigh Super Course that I want to convert from cottered to cotterless. The cranks I would like to install are Sugino "Super Mighty" pulled from a late 70s bike. What type of bottom bracket do I need to accomplish that? On ebay I found a NOS bottom bracket listed as "Shimano Deore XT Bottom Bracket 36X24T 70X122" for $20. Would that work? Thanks.

Do you have the spindle from the bike you pulled the Super Mighty off of? If it came off a bike with a 68mm bb, just exchange that spindle with the cottered spindle.

not necessarily that easy:
https://www.sheldonbrown.com/raleigh26.html#bottom . i haven't done one specifically on a super course, but most of the early ones i've seen have the same bb setup as other cottered models.

What kind of crank is on the bike know! 1st) You will need to determine the threading of your current bottom bracket. Is it english, french or italian threaded? I tryed searching a chainline chart that showed the Super Mighty but wasn't able to come up with one. Sheldon Brown could probably answer that for you.

I have done this. By some great coincidence, the whole BB assembly and cranks from a made-in-Taiwan Schwinn World Sport (1980/90?) fits exactly into a Raleigh frame.

Years ago (probably fifteen) I did the exact same thing to my early seventies Super Course. I removed the Stronglight cottered steel crank and BB and replaced it with a Sugino Idol cotterless crank from a totaled Azuki. Should be pretty standard stuff with english threading. Just don't do like I did and get rid of the original parts.

FWIW, I fixed a Super Course Mk II (1974) which came with Stronglight 93 cotterless cranks. Mine was built in the Carlton factory and has a 68mm English BB.

I also picked up a 165mm Sugino Super Mighty crankset, which has a 144mm bolt circle.

I assumed that being Japanese it would have JIS taper, but when I tried them on a JIS spindle (checked the spindle on some shimano cranks to be sure) they barely went on halfway.

I ended up getting a Campagnolo AC-S BB with 111mm symmetrical spindle and ISO taper. They're cheap (AUD$25), alloy cups, solid steel spindle. AC-H has a hollow spindle. It requires a special tool to install (eg Park BBT-4), your LBS may have one.

The BB you listed is 70mm shell, which is too big, and 122mm spindle, which is most likely too long.

Fixed gear specific:
Unfortunately the 111mm symmetrical spindle puts a 42mm chainline exactly centred between the two rings for the Super Mighty crankset, so I would say that the 111mm for triple crankset would be right for the inner mounting position, or a shorter spindle if you can get them in the US. That said, mine's been fine on both inner and outer positions for 800km with nary a hint of derailment.

68mm is english

70mm is italian.

im doing the same for a Styer, im just having the damnest time getting the cottered cranks off.

here is sheldons way of doing it:

https://sheldonbrown.com/cotters.html

and here is his page for sizes:

https://sheldonbrown.com/gloss_bo-z.html#bottom