I'd recommend keeping those sway bars, and adding 550 lb-in front springs and 4 1/2 leaf mideye rear springs along with some good shocks (Konis or KYB gas-a-just, or whatever your choice is). Also, rollerize your front suspension (opentracker racing products is good for that) and a Shelby drop of 1", and add traction bars in the rear (I'm using Traction Master style bars, requires some welding). A panhard bar out back is also a good idea, as are subframe connectors. One thing I've seen is filling the foot area of the floor pan with steel plate. It'll add some weight, but it'll improve rigidity. All this will provide you with a very nimble, yet streetable Mustang that will show up many cars at an autocross.
Proud owner of a '65 289 coupe w/ C4 (for now). Equipped with Edelbrock Performer intake, 600 cfm carb, Comp Cams Xtreme Energy valvetrain with XE262H cam, Hedman longtube headers, MSD ignition, and ported heads. Suspended by 600# 1" drop front and stock rear springs, KYB shocks front, 1" front sway bar, 1" Shelby drop, Griggs Racing GR350 rear suspension. Many more mods to come!