best vintage 70s, 80s amp?

I like
Carver
Luxman M-4000
Tandberg 3000 series

You may want to consider some of the 90's-current amps as they may require less upkeep. 70's-80's amps are a great deal untill they blow up. A 30-40 year old amp is kinda like a time bomb waiting to blow. It might pay to spend a little more and get something recent from Parasound, CJ, ARC , Bryston There are so many great amps to choose from.

For example I sold my Tandberg 3000 system which I loved and exchanged it for a Krell 400ix and a matching Krell CD 280 I think. This is my son's system and I wanted to get him somthing that was less likely to require service and if it did I know from previous experience that Krell in CT has a great service department and has reasonabe repair rates unlike Harmon Kardon's Mark Levinson for example but thats another story.

Again, what is the motivation for going "vintage"? Also, if you want something from that time that is not likely to blow up on you, I would get a point-to-point wired tube amp like Quicksilver which can run almost forever with some inexpensive capacitor replacements and a new set of tubes and you are almost as good as new.

One of my favorites from back then is the Mission 776/777 combo. No detail by modern standards but punchy as Cassius Clay (time appropriate). Combined with Altecs or Klipsch horns, it could hurt you. Ahead of it's time in many ways. First battery powered preamp.

There were some rare Yamahas and Kenwoods that broke through the consumer electronics barrier but beware of obsolete FETs.

That's easy... IMHO it is the ARC D70 in either Mk 1 or Mk2 versions.
I used to own a Hafler DH220...NOT even in the same league as the ARC.
The ARC is one of the best tube amps I have heard and i believe it will stand up against most any tube amp, even by today's standards. May want to read my review in the review section for more info.

What speakers will it drive? How big a room will it be in? Need more information in order to provide a recommendation.