Terry,
All I can tell you about the engine oil drain on the prototype tractor is that it was on the engine when I bought the tractor. That tractor was one of 10 prototypes built at the Louisville plant between 5 and 14 October 1960. Those tractors were sent to Engineering Test Center in Hindale, IL. 6 were to be tested/used by potential buyers, 1 was used to develop shop and owners manuals, 1 used for advertising material, and 2 used by allied equipment manufactors. When the test center was through with them they were sold to engineers or were destroyed. None were sold to the public. Frank G. Majer was the engineer that bought 409. He continued his own testing with it and kept a log of any problems/difficulties experienced during a full season of use (71 hours of operation) in 3rd gear, full throttle. He and his family continued to use the tractor until I bought it in 2003. Replacements for broken parts came from the test center or IH stock, and a number of replacement parts that Mr Majer had "stockpiled" came with the tractor when I bought it, parts that he determined to be problematic, including a new frame. The engine in that tractor (original) has a spec number of EX 28542E, and according to Kohler, the EX prefix was used on expermential engines during that time frame (oil pan IH used was/is different than what was normally used at that time). So, the 45 degree street ell screwed into the block for the oil drain could have been installed by Kohler, or it could have been installed by Mr. Majer as a way too keep the oil from running all over the frame when changing oil.