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It is my understanding that "detergent" and "non detergent" are references that are meaningless in today's world. All modern oils have a chemical substance to keep foreign things in suspension to be trapped by a filter, aka "detergent". If you don't run a filter, just change the oil more often. Those terms harken back to the days of paraffin-based oil which was crap compared to lubricants today. I guess if you like sludge or miss it, the old "non detergent" oil would be your choice if still available.
I do have 1 flathead car out of 5 without an oil filter, A multiple Dearborn recipient, that gets regular oil changes. Every flathead I have was rebuilt, and clean to start with.
If you have an old high mile engine already full of sludge, I would disassemble it and clean it out and put it back together if it had no issues.
My 2 cents.