273/ 2 barrel camshaft options

I guess that depends on your definition of "smog motor". They had both with and without C.A.P. which is an early stab at smog control. Granted, the engines are built the same, but, are tuned slightly different. The carbs are jetted and adjusted slightly different too.
I don't call a hose to the air cleaner and a slightly leaner carb a smog engine, everything else being the same. Look at the mid 70s engines and and up for the changes made. Those poor gutless engines.