LT headers make nice HP #'s on the cobra's . They are just a pain in the ass to install . You can go with a shorty header and still see nice gains and keep your current set up . And like Mars_302 said if you get LT's you will need a new mid pipe to match up .

Oh , and one other thing . Once LT's are installed you wont be able to remove your tranny without taking off the headers . Just something to think about!