Headers?
 

What are better, long tube or shorties?

Depends on the application. Stock cars will see a little gain from long tubes but the installation and subsequent hassels (reduced ground clearance, removal to change clucth) make it not worth it. On a S/C car, long tubes will make a huge difference over shorts. Just depends on your power level and what you are willing to deal with.

So if I'm goin for 350-400 hp, which should I use?

hmm
 

some people have problems with the long tubes being too low, hitting speeds bums and such, also clutch cables being burnt out being so close to the longtubes if you have a manual trans.
If your pushing over 350 at the wheels, long tubes should be better, of course it all depends on your combo!

if you have the extra cash then def go for the long tubes..they will net you more power no matter what motor work you have and IMO are easier to work with and around

long tubes on mustangs are what NORMAL headers are on just about any other car, at least the older muscle. Most people put headers on the older cars cause they come with awful exhaust manifolds... your mustang comes ffrom the factory with headers... better then any manifold i've ever seen... not that new headers are bad but if you could spend you money on something else you'd probabl see more HP gain from a K&N filter then from a new set of headers. Though if you're going to get a fully worked engine then the longtubes are probably the best bet, though they bring thier own set of problems like others said, ground clearance for one and installation can be rather frustrating
-as

i love my bbk longtubes but... dont get me wrong they are a pain in the rear. Since i have had them i think i know why i have replaced my header gaskets 3times probally because of the fact of them hitting the speed bumps and scraping all over the place and my car is not even lowered. They are also a pain if u need to change the clutch and other stuff...

later