My sister has a 2003 T-Bird and has noticed that there is nothing more that can be done to the engine other than a supercharger to squeeze out any more HP. The car is very heavy because it is a convertible. Yes, the transmission is better than a stock 4R70W, but not worth the difference if you have a transmission shop custom build you a racing 4R70W with a trans-go kit and kevlar clutches and kolene reaction plates. I have blown my sister off the line quite a few times and she cannot even come close to beating me. Thus, Ford had a nice idea, but left no room for upgrades and modifications.
AED 9 PSI Supercharger, .30 over Forged Block with Manley H-Beam Rods & Pistons, Innovative West 10% Overdrive Crank Pulley, Thump RRR Tensioner Pulley, Cobra Crankshaft, BPE Racing Stage 2 Ported & Polished Heads, Crower Direct Replacement Cams, 70MM Throttle Body, MAC Cold Air Intake, 80 MM L-MAF, 38Lbs Injectors, JBA Ceramic Coated Headers, Metal Matrix Drive Shaft, Kevlar Clutch & Kolene Reaction Plate Transmission, True 2.5" Dual Magnaflow Exhaust (Cats & Mufflers), Griffin 1 1/4" Radiator, B&M Racing Trans Cooler, Hughes 2750 Stall Torque Converter, 3.73:1 Gears with Traction Lock Differential, Trans-Go Kit, Superchips Custom Tune for Supercharger, 17" SVT Wheels, Kenny Brown Suspension Enhancers & Eibrach Lowering Kit.