Knuckledragger
blowing chunks and grabbing porcelain
The first letter and number on a Ford part number is the year. A=194x, B=195x, C=196x, D=197x, etc, etc.
An E1 =1981. You'll see older part numbers if no revision was made up until the time on installation. Meaning if the part was installed in a 1985 you could see a part number for 1980. Doesn't mean someone put an older part in, just there was no change in the part design in the years.
Another example, I've been doing some of work on my '62 F100, I'm finding C1-XXXX part numbers all over the place. Ford was good at marking parts, and their date codes are nice and easy to decipher.
Thanks! I should have done more research to confirm the information I was quoting before posting.