when did ford switch to 1 piece rear main seals

[dastang2]

i thought it was around 85 or so but i just heard around 82, which is it.

 

[93 teal terror]

82

 

[Venom4.6]

82

Actually during the 83 model year was the first. December 1 , 1982 was the changeover date.

 

[dastang2]

so they do have 2 piece main seal cranks with an imbalance of 50 oz. i got a 69 block and i am in a dilemma here.