Early A's running magnum manifolds?

i was looking into the magnum manifolds for my 1965 plymouth valiant, was wondering how they flow and if anyone else was running that setup. also if the magnum manifolds work then why wouldnt the magnum headers? anyone know any useful information?

Yes magnum manifolds do outflow most other stock mopar manifolds.But I thought they didnt fit due to starter being in the way?

I also noticed he doesnt mention any casting #s.

So if they will fit an early A wiith a few mods,will the fit a later A?