Put some very top of the line headers on a BBC in a 55 that had 3/8" thick flanges but still had gasket problems about once a year. Long trips seemed to hasten the gasket demise. The 454 did not have as good a selection of contoured exhaust manifolds so went to smoothed and porcelain coated 427 425hp cast manifolds. No more gasket problems and look great. Pic is with headers.

[img]https://i.postimg.cc/BtPjZgp7/30-A-55-Nomad-027.jpg[/img]


Evan