I would just leave it as an oil bath. That was on option back then and lots better than the oiled metal gauze of the standard production. Bear in mind that the more expensive cars retained an oil bath air cleaner after the cheaper cars had gone paper. Otto would probably know when Cadillac went to paper. And heavy trucks had them into the 80 and changed when fleets wanted lower maintenance costs. Apparently its cheaper to pay for the paper filter than pay the mechanic to pull the bottom of the air cleaner, scrape the junk out of the bottom, clean it and pour in new oil. Also when diesels occasionally "ran away" they could suck oil out of the filter and keep on running even if the fuel was shut off. And by that time compression releases were a thing of the past so they couldn't be shut down that way.
