Excellent pics. On the '89 P'up there are two connectors the same size but the upper is blue and the lower one black. The wires are as you described in the lower (black) connector and the temp sensor tested fine; 1.8K at ambient air temp (90 degrees at the time) down to .28K when the engine was warmed up.

The compression test was a little less positive.

#1 - 170
#2 - 160
#3 - 145
#4 - 170

A squirt of oil raised the pressure in #3 to 150. A comparable squirt did nothing to raise the pressure in #2 so, Mr. Paget, you are correct sir. Now the question is how much more money do I want to put into a 16 year old rust bucket approaching the half million mile mark...?

Anyway, knowing from past experience that it will run forever (short of hydro-locking) I'll do some watchful waiting, stay off the hi-way and repeat the test in a few weeks to see how fast it's deteriorating. Thanks to all for the tips.