Hello.A good rule of thumb on that is,if your car has an engine code of U,F,or D,then it's a 64 1/2.If the engine code is T,C,or A then it's a 65.Also the production date of your car should be before mid august of 64.There are a lot of small differences in the cars,but many were carried over into the regular 65 production year.The car should have a generator instead of an alternator,things like that.You could do a search on the changes that were phased in.Hope that helps.
Nice pages , will help me with my car . I knew there was some differences but there are alot of tiny details . I was wondering why my timing cover has a huge plug in it , I thought it was because some one had done something stupid , but appartently they put the plug in there when the car is PCV equipped and not road draft tube equipped .
64.5's had color coded (to the interior) door lock knobs. 65 models had chrome knobs. The "Mustang" fender script was 4.5" long on 65.4 models. In 65 is was lengthened to an even 5". The generator is a dead giveaway.