Assuming that the CyberHobby kit is accurate, to go from an E to a C, you would need to:
Use a slightly smaller tail wheel (the C tire should scale to 350 x 165mm)
If there is a scissor link on the tail wheel strut on your CH model, it would need to be removed
Use a smaller main wheel (the E variant had beefed up landing gear, different from the D - not sure what CH would give you here but the C tire would scale to 875 x 320mm). The hubs were also different as the E had larger brakes.
Rectangular inlet scoop on the top of the nose, if present, would need to be removed.
Rear firing gun on the C had a hollowed out fairing on the fuselage for stowage. The E did not. IIRC, the Eduard kit gives you both styles.
Pitot tube on the C was an L-shaped affair mounted under the wing. On the E, it was a spear type on the leading edge.
Rudder trim tabs on some E's extended beyond the trailing edge of the rudder. Didn't on the C.
The supercharger intake on late C's and all D and E's was slightly longer and had the lower edge extended toward the front. Your Eduard C sports the early C version that is just a short, straight scoop.
There are a few other minor things but I think that's the main stuff.