I installed a set of TTI headers on a 440 Challenger, the tubes turned too close to the head bolts and wouldnt meet the head! I called TTI and received a very arrogant response until I sent them digital photos! They offered nothing!
I installed a set of Hookers on my Hemicuda, good fit.
I installed a set of Dougs on a Camaro, good fit.

Best advice..A. thin flanges will leak for sure!
B. unless your building big power use HIPO manifolds!