My humble opinion... if the knock is loud enough for your neighbor to hear it... it's too loud. And it won't take long to get louder.
The oil pressure on my old 235 and even my old 261 was higher than what yours is even when both engines had many miles on them.
How long does it take for the oil pressure to come up on the gauge?
It sounds to me like it is related to the oil pressure, so I would look at bearing clearance. Especially main bearings.
Did you put the rubber seal in? Did the main bearing cap get torqued correctly?
