Adding an oil pressure gauge

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Congrats W.M. the bike has an oil pressure regulator which maintains pressure at a set level, depending on which part of the engine you want to monitor you may find a place downstream of the pump which is meaningful to keep an eye out for.
Also adding something to the oil system may increase the risk of that part failing and causing a problem but judging by your nickname you would be familiar with that scenario.

I think popgun had a diagram of how the oil is routed in our bikes, it may not be what you expect since the sparkplugs are oil cooled too on our bikes, maybe he can find it again or you can search for it with the search at the top of this page.

And since we are in oil territory i would add a warning not to use these k&n oil filters with a hexagon nut spotwelded to the top to make it easy to remove them, they fail spectacularly on a regular basis and this is well documented if you did not know this already.