1957 - 62 Main Diaphragm Covers are identified by the twin towers. Only one of the towers is drilled and tapped. These covers are made from a high strength Amuminu aircraft grade allow. The added strength will help maintian the covers flatness.
1963 - E1964 Main Diaphragm Cover
1963 to 1964E Main Diaphragm Covers are identified by having only one tower and a boss where the second tower was in the earlier design
1965 Main Diaphragm Cover
1965 Main Diaphragm Covers are identified by having only one tower, no boss where the second tower was, and no recesses between the mounting screws. 1965 Covers were not reproduced because there were ample parts made for replacement purposes. They are available from a number of rebuilders.