If you have the 2v heads the flat top pistons (+2 to 4cc’s) should net you just around 10:1, and that should be fine. If you want more compression you will have to mill the heads (and intake manifold). If you have 10.5:1+ compression I’d run a minimum of 92 octane.
If you had quench heads you...
Edelbrock RPM or Weiand Stealth intake, 650 to 750 carb, electronic ignition. A gear would be a great investment depending on if you use it on the highway much, something like a 3.50 to a 3.91. Cylinder heads would be a great upgrade. Also, think about some under-drive pulleys and a windage tray.
I have a number of years worth of Mustang Monthly, Mustang Illustrated, Mustangs and Fast Fords, etc, magazines. If anyone is interested I will give them to you, just pay for the shipping. Otherwise they are going to the local library. Let me know.