Not many choices on exhaust for an early A-body with a small block... The left side early a manifold has that down spout area to get between the firewall and starter....
Very tight in there... (that's what he said....) :D
I have one or two in my stash for when I put the 360 in my 66 Valiant wagon... I will open them up a little in the ports with a die grinder for better flow...