Whats the condition of the Engine ? If its got no issues ... SPECIALLY crank and conrod bearing issues (what mechs call main beegin) and has good oil pressure (get it checked) ... you are good to go. Else a swap is the way to go.
Need to see pics to the see the condition. I kind of did the same thing myself few years ago, rebuilt the CB80, did a paintjob, a thorough interior clean up and restoration, etc.