Dont jump to to many conclusions. You dont need to pull anything down at this point. Make sure your oil is full,start the motor and estabilish immediately that you have oil pressure.If you have oil pressure and you have checked for the obvious things like plug wire off or a wire arcing on manifold or a cracked distributor cap or a bad rotor button, then its proberly safe to let the motor run until it warms up. In may clear up right away. If it doesn't add a qt of trans fluid to the oil and let it idle for aprox 20 minutes ,Dont drive the car until you change the oil and filter. I have been selling cars for a living most of my life, a lot of them older and I have done this many times.You can go to NAPA, autozone or whatever and buy an engine flush instead of using the transmission fluid. Follow the directions on the can. If this doesn't work ,pull the valve covers ,one at a time ,let it idle and watch the valves and rocker to see if you can locate the problem. iIf you do have to replace the lifters, make sure you put the whole (new) set in. Has anyone ever taught you how to adjust the valves? Its very simple on a small block chevy but if you dont know how get someone that knows well to show you. Good luck!