when one has dings that big in a piston the force has to go somewhere. Usually into the connecting rod. At the least you are looking at a head, connecting rod, piston, rings, and valves. If the guide or seat are damaged, or the bore scored then the engine is junk. By the time you price out all the parts, you are better off with a new engine or a good inexpensive one from a donor. I priced out parts on a high hour engine a while back that still ran. Parts cost too much for a rebuild to be economical. Good luck.