Sonny, I agree with Ron on the headers issue. As an additional downside, headers will fry the underhood compartment. You can try to wrap them with special wraos, but these are expensive and don't last very long. If you really want to improve your exhaust system, you could try buying some reproduction high rise exhaust manifolds out of Year One, but these are kind'o pricy at $500 for the pair. Also, these type of manifolds will make a larger difference at the higher rpm, while the relatively small cam of the stock 440 restricts high rpm performance. So, its hard to tell if the benefit is worth the $500. A dual exhaust is definitely recommended for both your 68's though. You will get a descent performance benefit out of this modification, along with potentially better sound. D^2 >I believe the Imperial is considered a D body I doubt you would find any >headers >listed for your car but from my point of view(a 25 year muffler shop owner)a C >body header should work BUT I would try to talk you out of it because of >all the >problems headers cause(blown gaskets,loose bolts all the >time,leaks,noise,etc.)If you still need headers I have found Hedman to fit the >best.I put a Edelbrock on my 68 and it worked great.I used the stock >manifold,save your money for gas and enjoy. > Ron > > > > > > > >