Adapting a cold air intake system in another BIGGIE.
Placing the cone air filter outside the engine compartment, in the fender well or inside the lower front spoiler are some good place for fresh cold air. Polyurethane motor and trans mount will help on launch and provide quicker response. Try and have the ECM/PCM re-flash with a lower 180 degree temp fan turn on. install a 180 T-stat when you swap the ecm/pcm. If the tuner knows what he is doing. By lowering the engine core temp will allow more spark timing and the fuel should be adjusted to meet maximum air fuel ratio. If you have a high compression engine or hi boost application. you will want to stay away from platinum spark plugs. During hard driving platinum are known to create hot spots in the cylinder causing detention/damage. Platinum plugs also feature a pointed/ needle center electrode. The center electrode will burn RED hot and sometime disappearing from the plug. I highly recommend AutoLITE 103 copper core spark plugs (hi-performance street only).Platinum plugs are self clean and are not likely to foul up. this is what make then last 100,000 mile. Copper core plug will not allow rich running condition, because the plug will foul-up and prevent spark/fire. A good tuning will keep any copper core plug running for 30,000 mile and no worries of hurting the engine from detention
A final gear sway will help on launch but will lose on top, you should find a set of gear like 3.42-3.93 which will give good launch and 170mph top end.
Mustang are animal/fast on cheap budget if you know what you are doing.