These precision laser cut 3/8" thick 304 stainless header flanges are manufactured in the U.S. and are machine surfaced. The adapter plate is bolted to the head with counter sunk bolts, and has tapped holes for header flange attachment.
The adapter plate has port sizing of 1.5" wide x 1.675" tall, the maximum allowed with a small block Chevy bolt pattern.
The header flanges are available in 1 3/4", 1 7/8", 2", 2 1/8", and 2 1/4" port sizing to allow for extra large tubing.