Yes, they are specific, and probably should be chosen by all the mods done to the engine after the fact. But who knows what that would mean? Nobody I know, and I've never seen a "conversion list" of characteristics to look for in a PCV valve when choosing.
So my fall-back has always been the same. Use the one specified in the original motor, in the original application. In your case, a '70's Galaxie.
I've done some experimentation though, where I found a smog-era 302 valve from a Granada would not work in my '71 Bronco 302 because it let way too much air in. They're always sucking a lot of air when they're sucking, but apparently there can be quite a difference.
To get the feature I wanted (90° 3/8" hose fitting) on the same size valve as stock, I chose one from a '71 Corvette with 350 because it was more likely to be a higher compression, less smogged engine application.
That one worked, as far as I could tell, just as well as the original one from the Bronco. No jetting or adjustments were necessary when I used that one. Unlike the one from the Granada 302 which gave me basically a huge vacuum leak that I would have had to re-jet richer and use more squirter to compensate for.
Instead, and you may have heard me talk about this before, that Granada valve stayed in my under-hood tool box and got installed every time I went up into the mountains above 4000' or so.
The goal was to take advantage of that "controlled vacuum leak" and not lose so much pep going up the hills at high altitude without having to re-jet the carb leaner for trips to the hills.
Worked great!
Between that valve and my MSD "Adjustable Timing" Dura Spark module (adjustable on the fly from a dash knob) my trips to the mountains were pretty uneventful after that.
No substitute for EFI or turbo-charging of course, but did the trick back then.
So anyway, not sure what parameters to use in your case. But the good news is that at least experimenting is cheap!
With an engine like that, maybe a mid-sixties high-compression muscle car valve?
Good luck.
Paul