Slant Six exhaust manifold, cylinder #3 header. There's a 1/4" pipe going thru manifold initial segment vertically (see pic below). Intended for an accessory or some pre-heater? The manifold has the early style heat exchanger flap counterweight. I don't know the origin of the manifold, it was half-buried in the ground in the backyard of the barn when I bought it.
Thanks for your help!!
Also be sure to check pics of my newly restored engine compartment...