Bruce, I did this just a few weeks back, including the GW pressure relief plug with temp sender and moving the pressure sender.  And I also had oil seeping from every threaded joint.  How much oil will drain as you re-do those?  Way more than is any fun.  My call – bite the bullet and drain the oil.  Just get a CLEAN oil pan, capture the oil and put it back in when you’re done.  Not much time lost and no rush getting it right.

Don’t know why you’re looking for pressure at 2-5 psi.  I hope to never see that.  What you describe sounds normal.  As to the grounding – when I re-did mine I used Teflon tape on every joint, now nothing seeps and the gauges are working just fine.  You could give the senders a ground wire.  Have the sender pass through a ring terminal and ground the wire somewhere handy.  But I’ve found that isn’t necessary.

From: Bruce Todd
Sent: Tuesday, June 22, 2021 9:08 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Oil Relief Plug

Anyway I plan to swap out senders but would like to know how much oil will
drain out from the open relief port...pretty much the whole 4 to 4.5
litres? or just a portion of that amount?  Please advise.

As well I bought an oil pressure switch relocation kit from Mansispeed and
have it hooked to an Intellitronix  pressure sender and digital pressure
gauge.  The kit moves the low pressure switch from between #3 & 4 cylinders
up to the top of the motor and near the t-stat.   I should be getting
pressures of 2 to 5 psi however I am seeing readings of 60 on start up and
then drops as the motor warms up to 25 to 30 psi.  Wondering whether this
is a product of the sender or its placement - or just how the gauge reads?

Lastly - any tips on stopping oil from lightly sweating / leaking from the
threads of the pressure gauge fittings?  Supposedly - not supposed to use
plumber's tape as it could affect the grounding and I have tightened the
fittings pretty snug - don't want to horse it much more.