FWIW .....
I was told by a really reliable mopar source that the seam was on the bottom.
However - it was offset to the center about 2-3 inches.
I have known this guy for nearly 35 years .... He said that most cars left with the seal/joint centered, but a good bit of them had the joint offset...
so .... who really knows ...
The thing he was really sure of was it is on the bottom.