In my last post I brainstormed a few ideas about an apocalyptic OSR Body Horror/Bio-Horror thing, along the lines of Stephen King's "The Mist", "Silent Hill", "Resident Evil" & "Doom" meets Lovecraft, Warhammer 40k & so on.
One of the things I briefly mentioned was choice of rules, B/X D&D or the 1st Ed. of "The Black Hack" being mentioned.
B/X is/was my first choice, as I really like the idea of reskinning the classes, and especially the MONSTERS and Random Encounter Tables.
One thing I'd forgotten is that there are at least a COUPLE of OSR Horror rules sets that could probably handle the job:
"Gary Vs The Monsters" is an OSR Horror rule set that I don't see get mentioned much, which is a shame. It's got almost everything one would need to run the style of game I was imagining, more or less. It's written a little more B-movie/tongue-in-cheek, but that isn't really reflected in the rules per se, so there's nothing to keep one from running it straight.
Other options could include "SURVIVE THIS!! Zombies!" or "Dark Places & Demogorgons" with a little work, & I'm sure there are others, but the first two are the closest to what I envision right out of the box.