340 Exhaust Manifolds on Early A-Body??

Measure the outlet flange where the exhaust pipe attaches.
I put a RH side manifold on a 72 Duster 360. Perfect fit and plenty of clear access to the oil filter. The RH manifold eliminates 2 bends in the exhaust pipe, which certainly helps flow. I couldn't get the LH manifold to fit with power steering, and I'm not going to manual.
To me it looks as if the LH "magnum" series manifold MIGHT fit a floor shifted automatic car with manual steering.