Best fitting headers

I ran the cookie cutter under the centerlink headers for years as that was all I could afford and the first good bump and the tubes would crush....I agree the Doug's we ran in my son's 73 360 Duster were the best fitting.
But I'd like to see a dyno test before and after squished headers. I remember seeing a GTX with one of the primary tubes beat to heck to clear the power steering box and thought OMG. The owner said the engine was fine, and I've read here that smashing those tubes didn't hurt performance. Now Im sure a big hp engine may show a loss with a smaller tube but I'm thinking a 400 hp engine it won't hurt as much if any. It'd be nice to see a dyno pull with a new set and a smashed set!
Maybe it's not such a big deal?