I've ran everything, my last attempt was a set of custom firecore50 wires, metal plug boot covers, perfectly angled boots, and kevlar boot covers from a Winston Cup car.
You're not going to enjoy the answer. Remove the headers, heat'em, bash'em, and wrap'em afterwords. You'll need 2" x 200' of wrap to do a set of longtubes for a BBM. Purchase your stainless zip ties from Amazon in bulk. Use advanceautoparts with coupon codes to order the (2) 2" x 100' rolls of wrap required. The newer titanium wrap is a bit more expensive versus the standard wrap, but it does not require any additional coatings and won't fade. BTW when you tighten the stainless tie, cut the remainder down to 3/4-1". Use needle nose pliers and twist the excess to tighten, rolling it into itself. This will allow you to not only have the tightest fitment, but will be safe to the touch as well.
https://www.amazon.com/010130-Titanium-Exhaust-Heat-Technology/dp/B0039Z5TIG
https://www.amazon.com/gp/product/B072WC1MXT/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1