Idle Rpm High in Park, Low in Drive

He put a load on the engine and it lost rpm.
That was because it was more powerful??????

When the engine is running in neutral, this is considered a light load. Engines can usually be run lean at light load.
When an engine is placed in gear at idle, say 600 rpm, this a relatively heavy load. Heavy relative to the power beig produced at that rpm.

The mechanism used to achieve timing under various conditions is NOT a true determinant of whether the timing is correct for those conditions. Many distributors are sophisticated enough in design that vacuum advance was only needed to adjust timing for leaner burning.

Your crusade against Chrysler (and other) engineers really gets tiring. @Newolddart is in this mess at least partly because he read that sort of self proclaimed "expertise". I really hope this thread does not become another one of your crusades. All of the previous posts have been pretty focused on things to be addressed.