OK, I got on doorman's site, and cross referenced the part to a 1990 Chevrolet C60, so maybe that will give the kid at O'Reillys something to go on. Also I found doorman's flange, but not the shoulder (pipe).

I'm thinking to cut a wedge out of the manifold and weld it back together. (MIG). Is this feasible since the manifold is cast iron, would it crack apart in use?