Great bikes---the best web resource is SOHC.Net--there is tons of info there, including forums, parts vendors, etc. Sort of the Pelican for SOHC.
The prices are all over the place, but you should be able to get a great example for 1,500-2,000.
SOHC has a year-by-year model difference/comparison section. Parts are not a problem.
If you want to CAFE it, there are planty of resources as well.
Here is the 76 that I did a mild Cafe on and my 78 Super Sport that is currently undergoing some mild conversion as well.
The 78 before and current condition:
