60-70 psi oil pressure?

Why the heck did the WD9's have such high pressure? My manual says 60-70 psi is normal. My 560 only runs
at about 35-45 psi. Also most modern diesels I've been around, namely my 444E in my IH truck, only run about 35-45 psi. What gives. Why such high oil pressure on an old low rpm motor?

IH must have installed a different guage in these old beasts too. Does anyone know if the correct guage is
41934-DC? I think the one used in the M's and H's is 41934-DB. I'm talking about the style with the small red band on the left hand side and no increments or numbers on it. The two guages look the same but have different letters at the end of the part number. The guages read differently, I tested them to a numbered guage.

Thanks in advance,

Mark