So I just pulled out the 283 engine from the 56 3100 and in trying to pin down the 283 exactly looks like it was used 2 years before it was built! Date casting
F 11 2 should be June 11 1962
block casting 3789935 61-62 car or truck and some listings show it used to 1964. 170-315 HP
The engine stamp code is F0612D . That translates to Flint June ,12 which matches the block casting date of June 11 . The D is a mystery as it is shown as either a 1958 283 with Power Glide or a 1960 283 with Power Glide . That means it was used in 1960 2 years before it was born?. . Looked at several different listings for date codes and all agree 1960 PG. I must be missing something, or it went through a time warp. back in time a couple years. Does not look to have been machined off and re stamped. Engine doesn't look like it has ever been apart.