Not trying to beg the point, but doesn't Kurt's report on emmissions make that clear? http://www.camaros.org/emissions.shtml
"In 1968 and 1969, the California and federal emissions requirements were the same and all cars were built to the same 50-state standard. The AIR system was installed on all L6 cars with manual transmissions, all small blocks with manual transmissions, and all Camaros with big blocks. (Chevelles and full-size cars with the 396/325hp engine and TH400 transmission were the only 68-69 big block cars to not have smog pumps.) Only the automatic L6 and automatic small block Camaros did not have smog pumps, instead they had the simpler Controlled Combustion System. Generally speaking, an automatic car required less aggressive emission control than a manual transmission car because the engine load (and carburetor fuel metering consistency) was more stable and predictable."
My 68 L30 is a southern car (out of Florida) but is automatic, so it does not have the AIR system. But if you want to restore it to L30/M20 (great idea, by the way) then the report says, "all small block with manual transmissions" did.