ARE YOU SERIOUS DUDE!? Put the crack pipe down!!

Regardless of worth, the 67 castings, which those are, were the worst flowing of all three years produced. The 69 was the best. That said, if you need um, you need um.
It takes a real moron to spend 4 grand on exhaust manifolds for an A-body. Maybe for a 70 Hemi Cuda, maybe.