I have to ask why long tubes over shorties?
In most cases and MOD motors the long tubes do not make enough difference to help.
In reality the headers in general are worth the effort as the rest of the exhaust is still the major restriction. Now if doing the exhaust along with the headers ther are gains to be had with some tuning. A stock tune will not see any real benefit.
So that the haters don't get mad at me everything work in conjunction, so to see a benefit you must package together your changes to be truly effective.
Headers, free flowing exhaust cai and tune will provide with an exceptional benefit. Doing 1 item at a time is no that effective and requires changes to the tune to get the most out of that bolt on.
Now from that perspective if doing headers don't forget the supporting items to make your mods the most effective.
Every mod motor I have worked on has been a problem child with the exhaust bolts. Soak sit resoak sit some more is pretty effective. Sometimes it still happens. An exhaust shop is your friend here.