Hello and welcome to the forum. Nothing like that Flowmaster sound, huh?!
. Right on! Stock heads, stock cam? Sorry, brother, but you are not going to see much difference with the above mentioned bolt-on parts. The gears will help a little bit on acceleration but they alone will not make it a different animal. Plugs & wires are a maintenance item that should be done anyway. A good set of Motorcraft or Autolite plugs and a set of 9mm SVO/Ford Racing (or whatever they call themselves now) would be a good start to a comprehensive tune-up. The headers, intake, exhaust, and TB are all good supporting mods but unless you are forcing air through the system, I.e., super or turbo charging and giving it the right amount of fuel, when the air hits the heads, the stock pieces are only going to do so much. How do I know this, you ask? Been down the same rabbit hole back in '95 when mine was brand-new, my friend. I have almost every conceivable top-shelf bolt-on mod, front-to-back, to a stock headed and stock cam engine and
on its BEST day was
barely able to make it into the high 13s. Now, it
will run over 140
real mph on top end but how often are you up there anyway? Point being, and not to be all negative to you or your aspirations, decide what you realistically want out of the car. Do you want a hot rod or do you want a reliable driver with a little bit of pep? I love my car but, realistically, a newer stock 4-cylinder Ecoboost Mustang would be its worst nightmare. It would probably embarrass me at the stoplight Grand Prix. I have spent thousands of dollars for it to be what it is and I am pleased with what I have but it's a grocery-getter compared to what's out there now. Now, if you are going to put the items you mentioned on anyway to help it out some then right on! Go for it! Please just keep this in mind from someone who has been where you are now and no, I do not know you or what you have planned so no offense intended; you cannot have a hot rod and daily driver in the same car. The more you hop it up, the more drivability AND reliability you will lose. The items you mentioned will indeed help it out a little bit. They will help it inhale, exhale, and will free up some choked-down power but it won't really add any. They will, at best, free-up what is already there and that will only be so much. Anyway, good luck and glad to help or offer advice in any way that I can.