The 2 cycle Detroits don't even have an IP. Still probably a good idea to add lube to every tankful, but I do that on my newer diesels (6.2, 6.5, Cummins 12V) too.
2 cycle Detroits do require the right engine oil, though. And it's best to buy it by the 55 gallon drum when you find it, so you...