http://i785.photobucket.com/albums/yy133/mustangking1/FE04069C-8C18-4C4D-9FBB-0D1B8AD4B6F7_zpsomlgrpfz.jpg

Hopefully the picture came through.

The engine is a 1978 460 stock everything. 83k original miles.

Why would the oil pressure be running high?

 

These old gauges are notoriously inaccurate.

 

I would hook up a mechanical gauge for peace of mind.

 

The factory gauge is meaningless. The sending unit could be bad. You'll need to read it using a mechanical gauge to know for sure.

 

My old 300i6 does this as well when it warms up it goes back more toward the "R", I never really worried about. Trucks been like that sense I've owed and it has over 300,00 which 50,000 I've put

 

When did you snap the pic? right after you started it? or after it reached operating temp?

If right after you started it that's "normal" to read high, then the gauge settles down after the motor reaches operating temp and the oil thins out.

But as the others have stated the factory gauges readings are pretty meaningless, they don't correlate to any real numbers, for that you'll need to install a mechanical gauge.