Thanks, volks, for your help!

Summing up (in case anyone has been tracking my issue and would find this
useful):

-I had an intermittent oil pressure light flickering (random, fast on and
off, twitchy, sometimes longer periods)

-switched the oil pressure relief spring with a part supplied by Porsche.
No change in troubles.

-got help from the list on the logic for the oil pressure light:
P less than 0.3bar = oil light;
P less than 0.9 bar + engine speed more than 2300rpm = oil light + BUZZER.
Great write-up on Go Westy:
http://www.gowesty.com/tech-article-details.php?id=42

-found my problem was a faulty wire on the low pressure [blue, easy access]
switch.  It was shorting through cracked insulation and caked-on crud and
corruption.  There has been zero recurrence of the oil light
flickering since fixing the shorting wire.

-installed an oil pressure gauge.  I went with the Condelli solution
because it seemed overall more simple and didn't require modification to
the push-rod tube cover.  Unfortunately, the modification did not go as
advertised: push-rod cover does not fit after the modification.  Possibly
there are compounding reasons for this disappointment.  Otherwise, I am
satisfied with this method.  The kit shipped same day I ordered it and I
received it the next day.
https://www.frankcondelli.com/staging1/store/index.php?route=product/product&filter_name=pressure+guage&product_id=1039

-Oil pressure at 4000rpm after one hour of running is about 26-29 psig.

QUESTION: why did my broken wire insulation suddenly start shorting?  Why
was it caked-up with oil-soaked dirt?

Answer: Because an oil seal at the front of the engine failed and oil is
finding it's way around down there.

Gabby
'86 Westy wbx, ~240,000km