Mopar Mistake 'Not offering a 273 Commando HP II 'option'

I think that, just by design, with that 3.625 bore it put it at a slight disadvantage against the 283 (3.875" bore) and the 289 (4.00" bore). Bigger bore offers less shrouding of the valves. Do the 340 exhaust manifolds fit on a pre-'67 car?