Fluctuating Oil Pressure (on high side)

Hey, I've been driving the Stang recently since I'm home for a bit and noticed that the oil pressure hangs around the O in Oil while at idle than climbs to nearly past the L when driving (doesn't matter rpm, just climbs) then drops back down to the O while at a light. I don't really remember it being like this, but last time I drove was in December. It's a 66 289 4bbl with original gauges, which I know aren't accurate. With the planes I fly, they tell you what to look for in fluctuating oil pressure or if it's out of limits, wish cars would do the same. Thanks for any help.

I checked the oil and it's good, just got it changed not too long ago. It's getting better now that I'm driving it more often. Gotta love old cars, real finicky sometimes. When I haven't driven it for awhile the first couple drives are a little rough but things smooth out with a regular cruise.