Haynes are usually provide pretty accurate information to rebuild your machine
however if you're doing a complete restoration on the BSA, try and get a copy of "BSA Twins Restoration" by Roy Bacon; that should tell you what each bike had cosmetically from year to year, and points out some of the pitfalls to watch out for
another great reference is "Modern Motorcycle Mechanics" by J. B. Nicholson - its quite hard to find, but well worth paying for
aside from those, i cant really help im afraid
