I'm sure i've seen a link with this info before but cann't seen to find it right now. my list show 1970 exhaust manifold numbers to be 233451 and 1238094 but 71 to 74 are also the same? I have a set that are numbered 233898 and 1383848 and have no idea what year they are? look the same but the 233451 has a little bump up in the top right corner (see photo) that pervents my heat shield that I got off a 70 455 electra from fitting on it. So if exhaust manifold 233451 is a 70 455 i'm wondering why my heat shield doesn't fit that one? are they different on electra's? The heat shield fits the 233898 manifold. are 1970 455 manifolds better performance then 71 and up?
