+1 on DFrost bringing up the 43.3mm chainline issue.

this might help. if you really choose to go this route, instead of just buying nice-ish crank and btm. bracket set off fleabay or your LBS.
it's an old Sutherland's manual and has pretty much everything you need to know or do to a pre 1993 bike and explains all sorts of bike "science" eg chainline, how to set up everything on a bike properly.
http://home.fuse.net/pieper/sutherland's%20handbook%20for%20bicycle%20mechanics.pdf