Rebuilding that engine will also depend on the conditions of the cylinders. If the cylinders are both within specs and in good condition, it might be worth rebuilding. You should have someone tear it down and check to see which parts need to be replaced or machined. It will also depend on whether you have a good machine shop in your area. Repowering a unit that size could easily run $2000, so you’ll have to spend money to answer your question. I rebuilt one that size two years ago, because the unit was in great shape, but the total bill was just over $1000. Bert and I are not standing next to you, with a glass of wine in our hands, to see the condition of the unit or engine. You will have to make that decision on your own.