Chevy 350 no oil pressure

I bought a 1993 suburban 2500 4x4 automatic it had 175000 miles on it and a 350 engine. It was smoking when I bought it not from the engine compartment black smoke. Not to bad but like what it would if you sprayed wd40 on the manifolds. I drove it 30 miles and the oil pressure was at about 50 at first then it dropped gradually. I passed a car and floored it and there was so much smoke that I could barelly see the cars headlights. I drove it further and the oil pressure dropped to zero and quit running. Is it blown and what do I need to do to fix it?