Oil Pressure Question

[Nixon1]

On a cold engine, my oil pressure is around 45 psi After it warms up a good deal...maybe for 30 mins of driving..my pressure at idle is only right about 20 psi. During cruising, it's maybe 25-30. Seems on the low side to me. During the period of time where the engine is warming up, I observed the gauge once. Pressure builds up by about 10 psi, and then sharply drops off....builds up again, and drops back off again. I leak almost no oil except when I run it hard...I believe it's coming from the front seal. I hear it's a common seal failure. And I burn very little oil.. All in all, I go through 3/4 to 1 quart every 3000 miles. The motor's got 144,000 miles on it and it used to be run on nitrous, not to mention the condition I received it in...ahhck...so yeah, it's been beat six ways to Sunday. So my question is...is my oil pressure ok for the age and all....and also, what could be causing this pressure build and release? Unless it's the gauge malfunctioning. I know american gauge clusters seem to be terribly built. I've never had a gauge cluster on an American car, either GM or Ford, that completely worked. Camaro had a broken Tach. The Stang has a broken Speedo. Which is more important is anybody's guess... Thanks guys.