Where to Install Oil Pressure Sending Unit on 90's 350

I'm not sure this one is new enough for the oil pressure to matter to the computer. Before I replaced the motor, it had NO oil pressure according to the switch (sat at 0 all the time) and it ran like that for over 7 years without a problem. This was also a motor that had been driven with the number one cylinder dead for over 15 years. This thing went through hell but was still running - and probably still would - without a hitch or a hiccup ever. But it was slow, shaky, and would fog any mosquito colony within a 5 mile radius.

Interesting factoid for the day: so this morning on my way to work, no less than 100 yards from the house, it hiccuped real bad - nearly died - and I noticed at that time the idiot lights and gauges were going crazy, and the voltmeter was reading about 10V (it was the only one working right). It was also idling higher than normal. I killed and restarted it two or three times and it didn't fix it like it had before... until it warmed up. I got almost to work; sitting in traffic I decided to try one more time and afterward I had 14V like normal and all was well. Left to go to lunch and it did the same as it did this morning. It even died this time when going from Park to Reverse. Kept on all the way to the restaurant; after I got there I shut it off and restarted and it was fine, and it did fine on the way back after sitting for about 45 minutes or so.

Long story short, I think it's a wiring problem somewhere but where I don't know. I put a new starter on back in July and no problems until two weeks ago so I'm wondering if I have a loose wire on it somewhere. But that doesn't explain the temperature thing to me - it doesn't do it when it's fully warm, only when it's cold. I also have a knock sensor issue but have been too lazy to crawl under it and replace it yet... surely that wouldn't cause this issue though I wouldn't think. Anybody got any ideas or seen this one before? I haven't ruled the alternator out either, FYI. The only thing that makes me think it isn't the alt is it's been a sporadic thing, however I'm beginning to think that's changed now. I've got an extra one so if it comes down to it I'll just swap them out no harder than it is.

Reminder - 1990 truck with a 1989 TBI 350 that's been rebuilt but still completely stock, and hasn't had any issues until this came about. It's still drivable, it just worries me. I'm going to look over all the electrical connections this afternoon after I get it home to make sure nothing's worked its way loose since so many of the clips broke when I swapped motors.

Where to Install Oil Pressure Sending Unit on 90's 350

Source: https://www.gm-trucks.com/forums/topic/115361-oil-pressure-switch/

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