65amp wiring/trouble shooting

I don't quite understand. The original VR in my car I had to replace has the parts number 3438 150, just like the one on top. But the 65amp had a different VR?
The replacement is an SMP VR125.
That is correct. The part number of the regulator you removed was in 1973 parts book as used for all Chrysler alternators.
The '65 amp L/N' alternator listed in the '73 parts book was not made by Chrysler, but by Leece Neville and has slightly different wiring.

I took look at Hamtramck Historical's Library, and the '74 sales books list the alternator with defogger as '65 amp' like you found.
See page 15 The 1970 Hamtramck Registry - 1974 Dodge Dealership Data Book - Dart
It's a confusing naming convention and its not standardized.

If your car's alternator is original, the '74 Service Manual shows
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Those tags made it easier than looking upo the part numbers.

Note these ratings are just names. They very roughly indicate the maximum that they can provide.
For normal driving, they only need to keep the car running, which is around 5 to 7 amps for your car.
With headlights, wipers, heater fan on, the demand will be closer to 30 amps.
The electric rear defroster draws alot of current just by itself, that's why your car got the optional alternator, heavy battery, and wiring modifications.