Jimbo, when you say "chromed" (cylinders and rings), are you talking about what would be called 'hard chromed' in an agricultural context? The bright, shiny stuff that's super abrasion-resistant? If so, there was lots of hard chrome in the converted (to run on natural gas) 454 Chevys and industrial Cummins and turbo Cats I used to run for well pumps and generators. If it's hard chrome, that alone will make them use oil.
With the kinds of displacements, rpms, and power outputs being discussed, one wonders why a diesel engine-type construction would not work. Tractor engines work at above 80% output their whole lives and it's quite common for one to last in excess of 8,000 hours before a rebuild. They're warranted for 5,000 hours. They don't need hard chrome and they don't necessarily burn much oil. And yes, some are air cooled. See Deutz's wares.