I'm pretty sure there is a catalytic converter warning indicator on the center dash, across from the low fuel indicator. If the floor gets too hot, the light turns on. I have a non-california '76 and there's no indicator there, just a blank cutout for it. Thats the only superficial thing I can think of off the top of my head. There's other things, like the ignition system is slightly different, but I don't want to grab my manual to check.