You're kidding me right, that is why most folks are here is to mod their car with Ford or quality aftermarket parts (IE: not ebay..) to build their own unique car? That's what 90% of the posts here (minus the horde from OT) are about - modding cars, and getting people's opinions on said mods.
You can change the car quite a LOT in the garage, actually..
Don't get me wrong not biting at ya, just sayin'. If it's how you like it - that is always what matters of course!
Kidding you...no, youi can after market a "Premium" just as much as any other model.
I didn't want to have to buy 19" tires, not as available as 18" and much more expensive. But I'd like to have all the other upgrades of that package.
and you see, that was my exact same issue. I ended up buying a base V6 manual trans and buying the parts as they come on sale from American Muscle. I just ordered the 3:55 rear end, its on sale this month at $159.00!!!
Eventually I'll end up with my own creation. But thats why i bought a Mustang.