I’d keep it. Once bitten twice shy? I can understand your nervousness about keeping it but the optimist in me would say lightning never strikes twice. As you’ve said, there’s a lot of cars out there that aren’t as well kept as yours and with a higher mileage and you don’t know how they’ve been cared for.
You’ve just invested a considerable amount of money on a replacement engine, so IMHO it makes financial sense to get a return on your investment and get some use and enjoyment from it. Also, if you were to sell or part exchange your car against another car, I doubt you’d get any more for it than you would for an equivalent car still on its original engine.
Enjoy it and don’t overthink what might happen because the chances are it won’t

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