I don't know about your rpm shaking problem, but you can look down the spark plug tubes with a flashlight, and see if there are two seams. If there are two seams (valve cover, rocker arms), you have the engine with the o-rings under the rocker arms.

 

Thanks

Please advise on my radiator problem

 

Replace the radiator cap.

A new radiator cap will allow the radiator to release pressure at some set pressure, so there is little chance of the radiator blowing up.