1985 and older mustangs had the smaller 10 inch flywheel
1986+ had the bigger 10.5 inch flywheel.
the tko uses the same size flywheel and disc. The difference is the spline count that goes through the center of the clutch disc. If your current clutch is good, you can keep your current pressure plate and just get a new disc.
tko clutch discs should be dime a dozen. All you should have to do is contact your vendor of choice, whether that be spec, centerforce, ram etc and tell them you want a 26 spline clutch disc for use with the tko.
additionally, don't forget that your driveshaft yoke is gonna be different too, so you're gonna have to order the 26 spline yoke, and swap yokes on your driveshaft.
In short:
-reuse the oem flywheel
-difference is in the disc, not the pressure plate. Get a 10.5" clutch with a -- -26 spline clutch disc, and the regular pressure plate
-swap driveshaft yokes