What Dave's saying is that Chevy never used this bolt on any original engines. If the engine you have hasn't been molested, then It doesn't have, and will not need this special bolt.
If it has one of these bolts, it would be the center one on the passengers side of the engine, right next to the oil tube that goes to the rockers. I think they were marked with an "O" on top.
To be sure of the situation, check the year of your engine block. if it is a 59-62, then the rocker arms should have an oil groove that is offset to one side. If the groove is dead center, it has the older rockers, and would need this bolt and plug, OR preferably get the right rockers. The cylinder head itself has nothing to do with this. If it is a 54-58 block, then the bolt isn't needed and the rocker type doesn't matter as the flow is controlled farther upstream in the system.
If you have a 59-62, then take a look at a shop manual. It has some good info and pictures in it concerning how the oiling system works.
