>I want to start with the older stuff like Grendizer
I mean you can't really go far without saying Mazinger and Getter robo if that's the case, although I think most people would argue in favor of the manga instead of the anime in both situations.
It's not "mecha" persay, but Captian harlock and Space Battleship Yamato sort of trail blazed a good number of tropes and you can see it's direct influence in early Gundam/Macross/Ideon.
Raideen isn't completely finished it's slowly being churned over by a /m/ subgroup that was probably killed by subninjas a few months ago.
Zambot 3 is really fucking interesting, but it's not very good. The animation is beyond terrible, but it does a lot of unique things I haven't seen in anime before, it deals with the displaced people after giant robot attacks, and at one point the main villain does some pretty brutal things to the population of earth. It has a great ending though, it's a very tomino show though.
I really haven't seen much of the 70s so I'm sure some other /m/an can give you better advice, but that's about everything I've seen in the 70-79 timescale I'd recommend.
