need help with choosing headers

To keep the X you would go with shorties. Not as much bang as long tubes but better than stock. I really don't have any experience with headers yet but I hear Bassani makes a good piece.

What are your reasons for keeping the X? Long tubes would be better and since it is a major pain to swap headers on these cars why not swap the whole thing from headers to cat back?

BTW...Welcome.
 
Go with the shorties then. Catbacks are hit and miss because they are generally different for each person depending on their taste. I've found the X a little too raspy for my liking. The H or the Prochamber I have now have a real nice throaty sound with the stock cats. You can get an x that will fit with LT's...just leave that catback. It will fit fine.

Try this site www.mustangexhaust.com and listen to some of those clips. You might find something you like.