i know that on tv on saturday or sunday mornings they have a bunch of car shows lined up. in one of their shows they have a 65 red fastback ( 65 or 66) and they install a shifter. of course they made it look pretty simple. maybe someone else reading this will know what show i am talking about. i believe it is on tnn.
Installing a shifter is not overly difficult. One thing to you did not mention is what tranny you have. I don't know if the fmx was used up in the 72 mustangs. The hardware that comes with the shifter does not support that tranny. if you've got a c4 or c6, then go for it.
Member: Slightly Modified
66 coupe 302
66 fastback 351W
You have to watch out on some shifters. The universal, and even some "direct fit" (standard tranny) shifters won't fit, and you either have to cut out part of the trannsmission tunnel or get another shifter. Just a note, I hate people that cut huge sections of the tunnel out to put in a jimmy-rigged shifter.
I have a B&M mega shifter in my 72 Mach1 the only thing I had to do is screw in a steel plate over the old 4 speed opening. And bolt the mega shifter to it and like they said above if you got a c4 or c6 the hardware that goes on the trans. is a snap.