I have two carbs here, one from each of the cars in my sig. I know they're four barrel, but I'm not sure if they are E4ME or E4MC models. How would I be able to tell the difference, and can the 84 carb be rebuilt and put on the 86 LG4? Thanks in advance.

As far as I know there are minor deifferences in the way the mixture control solenoid and it's related hardware operates but you can install either carb on either car and it should plug in and work fine with the ECM.

OK cool. How do I tell which models they are?

I beleive ANY QJet with a mixture control solenoid is an E4ME carb.

If it's got an electric choke, it's an E4ME. An E4MC would have a hot-air choke, but I don't think there were any CCC carbs with hot-air chokes.