The vin # is 5R07C177968...the door ID is tucked away in my parts boxes, but I am sure that this Mustang is from the San Jose assembly plant.
OK that gives us a good start. There are many options as to what will work to reproduce these finishes. A good start IMHO for discussion and study would be the "What worked for me..." thread below of the products I use and have been recommending lately
IMHO I would not recommend Firm and Fast in the trunk if for no other reason the color that it comes in.
Finally, after applying sound deadener, was factory paint applied over the top?
Depends on which sealer and sound deadener.
IN short for a 65 San Jose
Rear wheel wells - before primer and exterior paint
Front wheel wells - Sealer before primer and black (no body color typically in front wheel wells. Sound deadener after the car is completely together (minus wheels and tires is best)
Trunk - Before (sealer and sound deadener) exterior color applied. Sound deadener shot onto panels. Tail light panel and those surfaces were either sprayed, applied out a chaulking gun or a combination of both depending on when the car was build.
I've been away at the Judges meeting will post some pictures of examples from your car's time period later this week if that will help