If you take a Lycoming O-360-A1A and don't change anything the tag is what the engine is - a Lycoming O-360-A1A. If you take that this same engine and install a set of Lycon 10:1 cylinders this engine is no longer what the tag says it is. The tag is the type certificate for that certified engine, if changed from that it's illegal for certified use. You must stamp EXP on the tag if you change the engine from what it was certified to be (for experimental use). If you install a certified engine and prop on your experimental aircraft the engine and prop does not change. They are still subject to AD's at every annual. Don't forget that an aircraft is A & P not just an airplane. The A airframe of an RV would always be experimental and not subject to AD's but the P powerplant is a different story if you buy a certified engine and prop. Most owners don't know this and I see illegal tags all the time on experimental planes.
In the case of this engine the OP's thread is about, if it were experimental he would not be required to do anything. He could change the prop and go flying, he could use those AD'd rod forever. The key is type certificate.