You could drop 25k into a 4th gen (or any car) to make it go fast, or have a perfect paint job, but you'd never get that back on resale. The fact is, modifiying a car does not add value in most cases. Sometimes it hurts value.
If you properly stored this car, it's value would absolutely increase over time. Would it fetch the numbers 1st and early 2nd gens are getting? Probably not for a while. But the only way this car would drop in value is by driving it as an every day car, neglecting it, or if economically things got so bad that it would be foolish to have a car that doesn't serve a purpose.
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