That is the route I went on my 72. I have seen pictures of them in 71-73 with the schock towers in place but it looked tighter than I wanted. I also wanted aftermarket coil over suspenssion and rack and pinion steering.
I'm not sure vintage air makes a kit for a 71-73 Mustang. I'm using vintage air in my 72 Mach I build but I am piecing it together. I didn't need a compressor because that came with the drive kit for the coyote engine.
Take a look at my build pictures in the project build threads. I'm building a 72 Mach I with a coyote and 6R80 in it. It is running an moving on it's own power. About ready to go back to the body shop to finish the paint.
It is now moving on it's own power. My engineering on the transmission cable, lever and cable bracket worked. Took it out for a short drive. The blue really pops in the sun. Being able to drive it really gave me the motivation to power through this project.
I welded mine all closed. I am using Vintage Air. The only issue with this is you need to run a remote windshield wiper motor. I would recommend on a car not as modified as mine to make some removeable plates in plate of the grilles.
It was a great feeling knowing I had it wired correctly and got the timing chains in correctly after I put in the billet gears. It is different not having to worry about a distributor 180 off or backfiring through a carb.
There will not be cats on this car. I am planning on making a shield for the ECU. Just haven't yet because there was a lot of wiring and ac lines to put in place first.