I had those engines on my 1977 42' Californian. They had the stock (barely) flyscreen air filters with a pattern of somewhat large holes in piece of sheet metal. Both my mechanic, who is now retired but was a career Perkins specialist who worked for a time for the factory in Britian, and the local legacy Perkins dealer who has sold and serviced those engines since the early 1980s, told me that there was no need to upgrade the air filter unless I wanted to go with something like a Walker airsep for a cleaner and (very slightly) quieter engine room. They felt there was no benefit to a better air filter for that model of engine, some of which were running for decades with just the factory filter.
They also expressed some concern that a poorly maintained modern filter, whether a very fine media or an oiled filter, woukd lead to a restriction that would never occur with the factory filter and could starve the engine of air leading to less power and more black smoke, etc.
They almost laughed that one (me) would think adding an air filter that was never there to an engine that had been in reliable service for 40+ years would measurably extend it's life or improve its performance.