340 Exhaust Manifolds on Early A-Body??

Forget 340 logs, that is expensive old school resto stuff. You want these, and if you can find them in 2 1/8 ID (older ones, these are 1 7/8 ID) your in like flynn...never ran them myself but I hear they outflow 340's in the 2 1/8 form from Ehrenberg himself.

What are these from?