I can imagine that you'd be little bashful about asking the LBS to help you decide what to order form Nashbar. The BB diameter is determined by your frame, while the spindle length is determined by your cranks. As already mentioned, a Raleigh from the 90's should have 68mm threading. And according to Sheldon Brown's BB size database (
http://sheldonbrown.com/bbsize.html#truvativ ) all of the Truvativ cranks use a 113mm spindle length. So, 68x113 should do the job.