First, let me just say what a great experience you provided for your son (and yourself). At 9 or 10 he now has a greater understanding of the principles of the internal combustion engine than 99% of the people driving them. Good for you guys.
I'm going to agree with Chiphead here (not that I disagree with Proffit :p ). If the 216 is running fairly smoothly and not burning oil, I'd leave well enough alone. After all of the work you two put into her, both you and your son need to enjoy driving the old girl around. If you're not planning on racing her, she should be fine. Now you can take your time researching and thinking about a replacement engine at some point down the line and still get the pleasure of driving to the lumber yard.
