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Perhaps I have not read this thread completely. Keep in mind, the round drain screw seal washers could indeed be stuck in the gear housing cavity, which is normal and OK. You don’t want to use two gasket/seal/washers though. I would have another look inside those housing cavities with a pick to see if the washers are stuck in there. Replace the washer/seals for sure, but make sure the old ones are removed from the housing, two washer seals can create a leak as well.
The correct part number for the OEM replacement washer/seals is: 311598.
Replace those other orings as well, use the OEM pieces, even though they are expensive. Be sure to lubricate the driveshaft splines properly with the OMC moly lube as well.
PS: those compression numbers seem “OK” for this engine. Your compression gage might not be accurate as well.