Depending on exactly when in the '70's your Raleigh was made, it is likely to have Raleigh's proprietary threading for the bottom bracket and headset. The bottom bracket will have "English" dimensions for everything except thread pitch (26 tpi instead of 24 for English threading). That is a deal breaker for fitting any new cartridge bottom bracket, particularly if you want to use a Shimano Octalink or an ISIS crank.
Sheldon Brown has a good article about these older Raleighs and what to do with them: Look here: http://www.sheldonbrown.com/raleigh26.html
I expect by the time you get the Raleigh set up suitably for your needs, the cost will exceed buyin a suitable bike outright. One possibility is too look for a good used Trek 520 or Cannondale T-series bike.