This is got to be THE MOST ASKED QUESTION!
Well let'* assume you were talking about swapping a series II SC for a series I SC! That still isn't possibleas the engine itself used a different type of SC! Now if you were talking about swapping a SC to a NA engine well, that is even more not possible for the before mention reasons from the other member'* posts!
Ty'* response does offer the BEST plan of action in my opinion (If that means anything, nowadays
The swapped in Series II 3800 SC & 4T65-E trans will fit in a older style Bonneville though!