I thought the 69 383 and 440 used a normal Chrysler starter? The 66-69 manual Hemi is different but I thought the 383's and 440's were normal.
I think at this point you should mock it up with all your 383 stuff on the garage floor and see if the starter clears the exhaust manifolds or headers you have.
As usual on Moparts there are 30 different opinions some wrong, some right.

Sheldon