Goood stuff! It was around the late 70’s OMC got rid of the retaining ring holding the cup on and started to use a small stepped bolt instead (12 – 24 thread). You might want to grind the head of the bolt down a bit so when the clamp is tightened, the cup is pressing on the transom and not the head of the bolt. A drop of thread locker will keep it from coming loose to.