I have a Raleigh Carlton 78 Supercourse. My frame looks pretty much like yours except for the chrome on the fork. Mine is copper colored rather than green. I used a Shimano 122mm UN53. THe 122mm length gave me the correct chain line. NOS Shimano UN** BBs show up frequently on eBay for ~$20. I think Sheldon Brown's Web site has a discussion of using the Shimano BBs on vintage Raleighs.