Originally Posted by
Andy_K
The question about the bottom bracket has to do with how it's threaded. I'm not sure if that was clear from the previous discussion. Most new bottom brackets use what's called English or ISO threading (1.37" x 24 tpi), some older Raleigh's used a Raleigh-specific threading (1 3/8" x 26 tpi) which isn't compatible. The thing to do is hope that you don't have that. Your LBS can probably help you figure it out.
I fear he does. I worked on one of these old Grand Prixs with a friend who wanted to make it into a fixie. The BB of that one was 26tpi. Best bet with that is to try and use the existing crank or at least the BB. You might be able to change the axle and keep the existing cups. Alternatively, a good LBS should be able to rethread the BB shell. If you want to stay 26 tpi, you could buy Phil Wood cups (in 26tpi) and use them with a BB that has removable cups such as the Phil Wood BB or a Shimano UN-72.
Good luck!