I called him about getting a set for my 82 CB650SC. Haven't pulled the trigger yet because I'll need to move a lot of stuff around to fit the filters. Gotta rotate the battery somehow and figure out a mounting solution for the ignitor modules, turn signal relay, starter solenoid, and regulator/rectifier.
I think you'd have similar issues with your 1980 CB650, but I'm not positive what the under-seat situation looks like on your bike. I just know its quite tight on mine.