There are "Left" and "Right" rocker arms on the 1500 and 1600. The oil hole is on the "left" or "right" when you are looking down at the rockers from the distributor side of the engine as if you were going to do a valve adjustment. This also can refer to whether the rocker is to the "left" or to the "right" of the rocker shaft stand as shown in the top picture.There are SAE thread and METRIC thread rockers. They are interchangeable if you also change the adjusting peg and nut.
All 1500s came SAE from the factory. The 1600 engines before R-40000 were SAE. After 35-40 years of head and part switching you could have either. A thread gauge should be in your toolbox. It's worth it's small price in headache reduction!
