Your 2nd paragraph spoke to me. We, as replica owners, recreate that feel and re-live that time when it was called motoring, which was an adventure itself. In a lot of ways it was a simpler time, and if jumping in your car brings you back to that, even for just a moment, that's what's important.
You obviously have more emotionally invested in this than me but you bring up some great points- for example, is a Porsche any less of a Porsche if it's been rebuilt or has other than factory parts? Is it still a Porsche when almost every piece of sheet metal but the vin # has been replaced? And, of course, there are more. Not being a Porsche owner these questions have no bearing in my life and I'll let more qualified souls hash out these (and other) soul searching dilemmas.
What's important to me is that there is still the opportunity to experience that long forgotten thing called motoring, where the wind is in (what's left of) my hair and I can feel connected with The Road (caps are intentional, and if you've seen the movie Cars you'll get it). I really need to get my bucket of parts up and running before the opportunity is taken away, as I really think my oldest will understand.