Squeaking Sound Coming from 225 /6

Ok, a bit of an update. I took the Dart to my mechanic last sunday and they got to it on Tuesday. I had taken the valve covers off, didnt see anything I could easily identify as being wrong, but with 50 pounds of pressure I figured I'd be good for the 1.5 mile drive. Before I drove it over, I left it parked, cranked the car, and revved it in neutral. The squeak did happen, but when I drove it I heard nothing.

After my mechanic looked at it, he couldnt find anything out of the ordinary and couldnt even get it to squeak. I tried again while it was at the shop and it didn't do it. Since that no longer seems to be an issue, I took that opportunity to have my mechanic rebuild my steering coupler with a replacement from Pishta and a rebuild kit from classic industries. It removed a lot of the play, but there's still a significant amount of play (about a quarter turn turning the wheel counter clockwise, none turning it clockwise) while rolling, and about half that when stopped. Some other parts of that linkage are definitely worn out, as I can grab the coupler and turn it and get that play to happen, so it's not there. Time to figure out what's going to be replaced to get my steering up to par (perhaps time to switch to 16:1 or 20:1 and get a not cracked steering wheel)

After driving it around 20 miles round-trip to make sure it was fine and get some measurements here are oil pressure measurements:
50psi at crank
50 psi while driving at operating temperature
20psi to 30 psi while idling in drive at operating temperature

Thanks for everyone's help, sorry there doesn't seem to be some issue that would explain it.