yeah not to be a prick, but your age is showing, i personally didnt get on here till just now, and it sounds like your yelling at me, which dosnt really make me want to help ya out. but ill put that aside, and not be a bad guy.
as far as your choice of cars and options, i applaud ya, very good choices, a bit powerful for a 13 year old in my opinion
but sweet none the less, wish i had a car like that at that age. anyway, for headers, i would go with edelbrock TES. exhaust, al about personal taste, i would go to as many webisites, download as many soundfiles, and listen to as many as possible in person to figure out which one you want.
as far as seats, the seats out of a fourth gen camaro or firebird will bolt right in, if you are pulling the carpet anyway, you can always cut off the seat studs, weld in new ones, and throw in a pair of C5 corvette seats. the studs are 14.5in wide, and 21inches long. i love those seats.
but seriously man, things happen pretty slow on here, its all a bunch of people with other lives, not people being paid to sit here and answer questions. so if it takes a little time, try not to throw a tantrum. people will get to it, and we will try to help you out. but getting all mad and acting like a todler will get you kicked off the forum. just a little friendly advice.