He rebuilt the engine, but can't put a valve cover gasket on, or change the spark plugs? That's like a 5 minute, $5 job. What he really means, is that it's leaking oil somewhere, and there's a slight chance that it's the valve cover gasket. And, the ignition system is probably messed up, or there's oil fouling up all the plugs, so you have to replace them every couple hundred miles. Anyone trying to sell a car that seriously only needs spark plugs to work properly will spend the $5 on new plugs so the car works.
It's pretty clear that he cares more about the visual aspect of the car rather than the performance/maintenance, which means he probably spent all the money on making it look 'nice', rather than keeping it well maintained. For all you know, the 'rebuilt' engine could just mean he changed the oil on it once. I guess that's kind of like rebuilding the oil level in the engine.
Personally, I wouldn't do it. The typical person who spends money to make their car look like that also tends to drive it hard, and put more wear on the engine and transmission.
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