Hello imacbo: The Ford VINs are all consistent in their design. You can go to
LOVEfords - Information for Ford, Mercury, Edsel, Lincoln - The Blue Oval and vist the "tech Library". There is a VIN decoder for all 1960 to 1980 Cars.
You are correct in that the first number is year; 2nd digit is Assembly plant - S for Allen Park, Michigan; 3rd & 4th are Body series code - probably 42 not 4Z. In 1968 42 was a 2 door hardtop; 5th is engine code F is a V8 302 CID 2 barrel carb; and 6th thru 11th are consecutive unit numbers.
I did this to decode my 69. Good luck
