I Need Help In A Bad Way!!

[Matt_ks]

So this past weekend I bought a 82 chevy pick up with a small block 350. The problem is it smokes. When I leave a stop light it leaves a gray cloud behind, and as in driving down the hiway it smokes like a 2 stroke motor, but it dont smoke on start up and while its idling. The guy I bought it from swears its just the valve guides and seals, but my father-in-law says its the rings. the kid also says that he had two mechanics look at it and the believe that its the heads also!! CAN u guys HELP???? I dont want to buy a new motor if I can just change the heads!!