Thanks, Dennis:
Your description matches my suspicions. In the 1.9, the oil temp runs open
loop, warms up slower, and cools only to the extent that its flow through
the components of the water cooled engine block allows.  The crank acts as
a cooler until it reaches a steady state temperature, but could act as a
heater if loads and speeds create more heat than can be given up merely by
circulation through the engine.
In the 2.1, the water warms up quickly through the closed-loop thermostatic
system, and the oil from the pump is brought to that temp, which speeds
warmup early on and sinks heat from the oil into the water (and then on to
the radiator) if the oil temp should rise above that of the water routed
through the cooler.
No, I didn't align-bore the case, but I would have if it had needed it.  It
didn't.  The crank was well within spec as well, and so was the cam, even
though its bearings were hammered.  Let's hear it for filtered oil!  I did
have the rods rebuilt, though, as they were a mil or so out of round.
My 30 psi number is at 3000 rpm.  I'm not sure of my 4000 rpm pressure,
since I don't drive around at 4000 rpm.  If I was in a hurry, I wouldn't be
driving a Vanagon!
But I'm still curious - what kind of oil pressure does newly rebuilt, or
otherwise sound 2.1 engine generate at idle, once it is all warmed up?  Are
the 12 psi @ idle and 40psi @ 4k rpm numbers typical of both engines?  How
much difference does the oil cooler make, after the warm-up cycle is complete?
Thanks again-

Paul