I owned a 73 for a long time. They're heavy, not very powerful and have vague (recirculating ball) steering. They are pretty reliable, however. You can buy parts pretty inexpensively and they're not hard to work on. They are very well made and the parts are very high q. An enjoyable ride but not a sports car- but a nice GT IMO.
But I would steer clear of a 1980. I would either get a newer 560 as advised or (my preference) look for a 72-73 350 or 450 with a manual transmission. Around 10-12K for a decent one. The six is almost as powerful but weighs a lot less. And get one with the European bumpers and headlights. I redid mine, lost pounds of ugly fat and could see at night. I hate the US bumpers- they ruin the looks IMO.
