very low oil press., 90 s10 blazer 4.3

got a 90 s10 blazer, with a newer 4.3 motor.. all of a sudden the oil pressure is reading way low, and when i come to a stop it hits zero and the Check Gauges light comes on.. oil level is full and the oil is clean, it was changed less than 1k miles ago.. not sure how many miles are on the motor and/or the oil pump, etc.. it had a lot of work done before i got it, just not sure exactly what. any ideas?

If your not getting any noise from the engine when the pressure drops, could just be the oil pressure switch