What 360 letter codes in particular are you referring to?
In the 74 parts catalog two 360 4bbl vin engine codes are listed, J and L. The J code is for a California 360 4bbl and the L code is for the 360 4bbl Hi Performance engine. My 74 360 Road Runner is a California car and has the L code Hi Performance 360 so apparently the Hi Performance 4bbl 360 wasn't a 49 states only option.
E56(J) is the engine code (on the data tag) for the California 360 4bbl and E58(L) was the engine code for the 360 4bbl Hi Performance engine. I also did not see in the Model chart where the Charger SE was available with the E58(L) High Performance 360 4bbl. You could get the E57(K) 360 2bbl or the E56(J) California 4bbl. It seems only the Charger (hardtop 23) or the Charger Coupe (Coupe 21) were available with the E58 Hi Performance 360 4bbl.