What type of bolts were used to plug the AIR holes in the exhaust manifolds.
They were special hex-head plugs, P/N 3889330 for small-blocks, and P/N 444618 for big-blocks - Rick's has them. They were only used on units built for overseas export, as part of RPO KD1, Less Air Injection. The plugs were 1/4"-18 National Straight Pipe Thread (matching the threads in the manifold holes), NOT 1/4" NPT tapered pipe thread.