Are there many things to be very mindful of looking at used late 70's 80's cs or cc 27? Other than the obvious water stains, soft spots(which areas), engine mounts, bilge area?
Yes. All of the above and more. Here is something to read that will give yuo some more ideas about that. Marine Survey 101, pre-survey inspection
There is much more information out there.
In general as I don't know either boat particularly well, but I own a 1976 North Star 26 which is similar in design and build to the C&C.
Good signs: Boat is sailed regularly. Is clean and obviously well maintained (Owner has records of professional services, etc...) Motors that have sat for a while can be ok but can develop problems, and unused boats decay faster than active boats.
Important things to look for that may be deal-breakers: Evidence of water intrusion, particularly around the chain plates. Condition of the main bulkhead at the chain plates, if it's rotted, it's a big job to fix.
Keel bolts, bilge frames/stringers: Keel bolts and rods should be free of excess corrosion. Replacing the rods (J-hooks) on a lead keel is expensive, often exceeding the value of the boat.
Damage to the keel indicating a hard grounding. This can lead to all sorts of invisible problems due to the impact or inadequate repairs.
Stringers and frames under the floor should be Fiberglass or glass encased wood. Look for signs of water intrusion and rot, particularly under the compression post. My boat had an exposed wood stringer under the compression post that had rotted away so completely that it took a while for me to realize it had ever existed. It was a major structural problem I was fortunate to be able to repair. If it's a keel stepped mast, check the condition of the mast step, possibly metallic and corroded.
Electrical: Make sure you understand what you have. If it's all professionally wired, understand the condition and what maintence you will need to do, if it's a DIY ratnest understand what needs to be replaced. Most boat fires are electrical, and boats tend to burn fast, which is hard on the crew.
In any case, the boat will teach you boat systems. Just remember, the boat will teach you at the boat's pace.
Hopefully someone with specific experience on these models will chime in. Good luck!