The C body manifolds are unlikely to fit. The factory A body left manifolds had an upward design to allow clearance for the steering chuck. Standard log type manifolds were too close to fit, at least in factory installations.
I have been able to fit 318/360 type log manifolds in a few A body cars by grinding the ribbed areas. I have to grind on the power steering chuch as well. Manual steering would clear though. A factory type manifold is the safest way to go in regards to fit, function and originality.