Basically there are 4 heads. Two, the early heads have "domed" chambers and use domed pistons. The earliest of these has small ports. The "H" head Has 1 3/4" intake ports. The next two heads use a flatter piston and similar but not the same D shaped chamber. The 302 head has the large 1 3/4 intake ports. For those who actually drive their Jimmys the small port heads are actually better on he street. These engines were used in trucks that hauled heavy loads all over the world. Any of them 228-302 will do well in a daily driver.
