have a rebuilt 49 v8 20k miles on it ,runs great with great oil pressure. changing the oil do I need to take off the clean out plate off and clean the pan? the engine has an oil filter and have been running modern oils.
If the inspection cover is not leaking and you are not having any other problems, I agree with "Murre" to leave it alone. If you open it up, you are taking a chance of starting an oil leak as these have a reputation of being hard to get sealed.
If you are really curious about the oil contaminants, I would send a sample in and have it tested. Not that expensive and much easier than messing with the oil pan cleanout. It will also provide you a lot more information.