Agree with just about everything said, pro-headers that is. 
Tests again and again have shown that even on bone stock engines, headers work. Maybe not 40HP, but 10HP is noticeable and entirely possible on a 350. Long tubes are better than shorties, period, when talking power production only. Thorley tri-y's, in the ony back to back test I've seen, did NOT make more power than long tubes, less actually. My experience so far is that if you want headers to last, get stainless steel, because everything else eventually fails. Equal primary length is one of the least critical construction aspects of headers. You can make plenty of power without them being equal length. Scavenging still happens, that is based on a few things, one being diameter of the primary tube. Larger primary tubes WILL hurt power (because of no scavenging) this is probably where the "backpressure makes power" myth came from. Too big is bad, too small is bad. None of us here (that I know!) have the resources to play around with header design enough to actually know what our particular engine will perform best with. Unlike NASCAR teams. Obviously if you can get equal length, great, but if you aren't measuring power with different length collectors and so on, forget about it, the increase isn't worth the effort or cost. Probably have a hard time finding them for our trucks anyways. I don't know if David Vizards (excellent) article on exhaust is still over at enginemasters.com, (hardcore tech section?) but if it is, I believe that will shed some light on the subject.
Tests again and again have shown that even on bone stock engines, headers work. Maybe not 40HP, but 10HP is noticeable and entirely possible on a 350. Long tubes are better than shorties, period, when talking power production only. Thorley tri-y's, in the ony back to back test I've seen, did NOT make more power than long tubes, less actually. My experience so far is that if you want headers to last, get stainless steel, because everything else eventually fails. Equal primary length is one of the least critical construction aspects of headers. You can make plenty of power without them being equal length. Scavenging still happens, that is based on a few things, one being diameter of the primary tube. Larger primary tubes WILL hurt power (because of no scavenging) this is probably where the "backpressure makes power" myth came from. Too big is bad, too small is bad. None of us here (that I know!) have the resources to play around with header design enough to actually know what our particular engine will perform best with. Unlike NASCAR teams. Obviously if you can get equal length, great, but if you aren't measuring power with different length collectors and so on, forget about it, the increase isn't worth the effort or cost. Probably have a hard time finding them for our trucks anyways. I don't know if David Vizards (excellent) article on exhaust is still over at enginemasters.com, (hardcore tech section?) but if it is, I believe that will shed some light on the subject.
