You might try Doug's Headers.
They do offer a special design for 2-1/8 dia, full length for tall deck BBC in a 67-69 Camaro or 67-74 Nova
PN 776-D321
I went thru all this with a tall deck and raised heads in a 55 Chevy. After trying 4 sets (and return freight) I had some made. What a pain.....
Dave