Tried and liked:
Model F switches - amazing clicky switch
I was going to recommend beamspring because I think it would blow your mind, but like any other very vintage board they take a particular person. You have to be okay with a typewriter-like profile and the available layouts, paying $40+ for shipping, and finding the right one for a decent price.
I need more time on mine to decide, but I think a 3XXX metal-case beamspring would absolutely destroy my 4704 Model F. My 5251 with a plastic top case probably does too, but I'm a goddamned sucker for metal cases.
Tried and liked:
mx blacks (vintage) - 62g are my favorite
I like my Hall Effect quite a bit but off-center keypresses are brutal and they're not readily convertible to modern computers. I'm with you on 62g vintage MX Blacks, think they're still my ideal linear. You could try SKCL Greens, they're very nice but if you didn't like the actuation point of SKCM Blues I'm not sure I'd bother.