New! And some header questions..

Hello forums! I am new to this sight, but I have used it in the passed for various things.
So I am 18 years old, and I love mopars. I've grown up with them as my dad has always loved them. He actually has a 69 se r/t 440 4 speed charger that I helped him resurrect from our barn, and that has been a total blast. My first car was a 74 Gold Duster, slant 6 torqueflite, and that has been my daily for two years now. I worked a summer job and saved up and bought a 72 4 door dart with a 318 with a cam and heads as a replacement, as it is in much better condition, and has various upgrades that the duster was lacking. We are also doing a 4 speed conversion on it. Soon, I am hoping to sell the duster to pay for these things. So now onto the headers part...

Currently the dart has manifolds, but I want to make custom headers and exhaust for it. I am in the process of designing (and hopefully soon actually making) an un-intrusive 8 into 1 header, I don't know if you have seen the youtube videos on it but on youtube search "8 into 1 header" or "tanner faust passat," and you will quickly see why I want these. The reason I want to do this is to have something different, and that sounds wicked. I'd love to start a youtube channel on it to get my generation excited about older cars, because not many younger guys are!! So if I was to make these, would there be a market if I was able to connect with an exhaust shop to make multiples of them? And, unfortunately the primaries will most likely have to be much longer than the regular hooker headers (probably 40".) Will this be an issue for me? (my main goal is sound, but obviously a big second is performance.) I'd love to hear any comments or thoughts! Thanks!
-Nic