The oil pressure gauge on my 87 Cher Laredo Renix 4.0L is COMPLETELY topped out, like sitting at a 90 degree angle to the passenger side of the cab, not even reading ON the gauge. When starting or using more power (I think my alternator is starting to go - my "charge" varies from 11v to 14v) it does NOT move whatsoever, not even jiggle back-and-forth. I figured my pressure sending unit was to blame.

This is the ONLY thing I can find that even resembles a sensor around the oil filter :



And this pic shows the general location of where I found whatever that is:



I want to know if that IS my oil pressure sending unit and if it is, where can I get a replacement like it, because every other I've Cherokee uses one of these:

 

That is your sending unit.

The replacement one in the photo is for later years.

Napa.

 

I have seen the relief valve in the oil pump stick and go max pressure sometimes blowing the filter apart.