Velosophy

I’m looking for advice on where to find a compatible tapered spindle, for my old Carlton Corsa. I know sacrilege but it will be a single speed as I bought it frame and fork only and it has relatively horizontal rear dropout. Super excited actually I’ve never had a single speed. Already have the hubs/wheels. I did some reading on BB and I think the one in question would be considered an old Raleigh as it is 71mm shell. I’d possibly like to put an early tapered crank on it that I don’t have yet. Suggestions?

cyclophilia 

Begin by verifying the bottom bracket shell threading. Start with a pair of 1.370 x 24 British cups. If they thread correctly, you will have a wide selection of sealed bearing bottom brackets and can choose an appropriate spindle length to match your preferred cotterless crankset.

oneclick 

NB5204555 translates to:
Nottingham built Feb 1975, frame # 204555
That and the 71mm shell (and the thickness of the socket walls as they appear in your photos) strongly suggest 26tpi BB theading.
If so, and your cups are still good (or you can find some good 'uns) you just need an axle that will set the cranks the correct distance from the frame.
Otherwise you have a few options:
a) ream and tap for italian cups
b) turn italian cups down and thread them 26 tpi
c) threadless bb unit
d) Phil Wood
If not going with a) it may be worthwhile getting the shell reduced to 68mm as that will make getting an axle to fit easier.

And single-speed by itself has no stigma, it's the (unnecessary) dropout hanger-ectomy to which people object.

Velosophy

Ok no dropout hangerectomy here as it slides into dropout and is screwed on. Either way I wouldn’t as the ability to take back stock if someone wanted is important to me. The same reason I didn’t cut the fenders and add wide body kit to my 240z when it was the thing to do.

Velosophy

I do have the original cups I just removed and haven’t looked closely to see if condition warrants reusing. Threads are good on shell and cups though.