would a 65 mustang that is possible the last one built before switching over to the 66 model year worth more that any other 65 mustang?

Any definite answer would come from the museum. It might be more valuable if there was some sort of verification from Ford.

vin number could confirm last one built

I worked at Dearborn Assembly for 15 year and have never heard of such a thing happening. Not douting what your father says but as far as its value if it was "specially made" for him this alone doesn't make it any more valuable.

Only if you can prove that it is in fact the last one. The VIN would be able to tell you but make sure the engine, transmission have not been replaced.

I don't think it makes a difference if it was the first or last 65 built,however a 64 1/2 would be worth alot more than a 65..I still would love to own a 65!!also what code is the vehicle that makes a big difference..post a pic of your 65..Im looking at a 1965 ragtop,with a 289,4spd,decent body,good interior,the person is selling it for-$15,000..

I don't see how any car could be built after the line shut down, first of all there are 100's of people who work on the line building the cars so they would of had to be present for it to be built. if the car was builton the line, the line couldn't be shut down but it could have been the last car down the line before switching to the '66's. There wasn't much of a difference between the 65 and 66 other than minor trim. The serial number on the car will tell if it was the last '65 built when the line was up and running. I would get a Marti-Report at martiauto.com. The Marti report will tell all about your Mustang and actualy how rare it is, especially if the car was special ordered and built. I'm not sure if the Henry Ford museum would want your car or not but I'll take it off your hands if you want it to go to a new caring home. Kenny/MrBlueOval