I’ve had a couple of these motors apart since it’s the same as used on the Sperry Rand Tricarts. I recall having the same dilemma, but for me there was evidence inside the keyway as to which one was used. Unfortunately, I never documented this for future reference. Also I was surprised that there is no mention of the dual keyways in the JLO service manual. These motors can be assembled for carb front/exhaust rear or with cyl jug 180º opposite and could be configured to run in either direction. I think that this the is reason for the dual keyways.
Anytime I’m working on or hear about any JLO engine, I am always reminded of an anecdote relayed to me by one of the old timers that worked at the Sperry sports vehicle plant in Lebanon, OH. There was a massive fire there consuming most of the fiberglass production and vehicle assembly building and also a rail car full of these JLO L230 engines… he said maybe 500 or 1000 engines were lost. He described the aftermath as a massive blob of aluminum with crankshafts sticking out. :blink: