distributer cap mods?

Are you sure corrsion is what you're seeing ? The caps come with a lubricant on the contacts that is invisible initially. After use that lubricant turns to a white-ish powder.
It's very common for the novice to go in there with a pocket knife and scrape away all the lubricant.
Back in the 80s Ford had a problem with their pickup coils melting down due to heat build up in the 3.8 V6 distributers so the added a atmospheric vent to those caps.
I suppose one might hand fit that vent into a different cap. Its purpose wasn't moisture related though so...
To apply a small bead of grease where the cap meets the base was somewhat common for slant 6 owners too since that distributers location made it more prone to moisture getting inside.