It would be a cool bike to get and set aside,best to hear it run and see if everything works though for that price.
The 74 would be the one people lust after ,lighter frames,some good changes.
As far as going riding it would probably nickel/dime you to death keeping it going,hard to find parts to keep it going,and yeah,brakes back then were mere rubbing devices at the best of times,shifting is done soccer style with a long well placed kick at the lever,and even then they pop out of gear sometimes.
Two strokes have gotten a whole bunch better the newer they get,an old one like that would run pretty ratty compared to even a 90's 2 stroke.
I raced Bultaco's for 3 or 4 years and its an aqquired art to shift and ride them.
Some bikes around at times