I have the 5.7; and when truck is at idle the oil pressure guage goes to "0"...... upon driving the guage is where it should be at normal pressures.....what is going on.... clogged screen or oil pump problem??

Based on the age of the 350, I'd safely assume its got high miles. You are probably looking at a complete rebuild. When the cam and cam bearings wear out, the oil pressure will be high cold, but when the engine gets heat soaked, the oil pressure drops. Mine did the same thing.

I would screw in a manual gauge to confirm its low oil pressure and not a bad sending unit.

88-95 gauges suck, i would recommend that too, verify your reading before you get too far.

As others have mentioned, check your pressure at the sensor.