I remember seeing speedsters in the late '70s for $3000. When I cared again, it was Y2K, and a used replica was $15k and an original driver could be had for $40-50k. When I built in 2005, a new Intermeccanica was half of what an original went for-- and there was a guy on here who delighted in pointing out that "a guy should just buy an original, if he's going to burn money on an IM".
Old Porsches started climbing rapidly in value shortly thereafter - then hit the afterburners. Convertible Ds were next to run up the ladder, then early 911s, then 912s. 356 coupes (which were always the ugly step-sisters) have taken off in the last 10 years. When my eldest daughter was 16, a 912E could be had for less than $3000 all day long (I know. I tried to convince her to buy one). Even 914s are starting to move up now, especially 6 cylinder cars. VW Buses hit the stratosphere about 10 years ago, and I suspect that Ghias and Beetles will start to move hard as well (a nice, rust-free Ghia is now a $30K car).
The crazy thing is: they're still leaky, rust-prone, funny driving old cars. They're weird in the extreme. Any modern car is better by any objective metric.
I got into the hobby when I could've bought an original speedster with what I had available to spend. I could've bought 4 coupes for what I had available to spend. The thing is: I didn't want to. I didn't want a rusty, leaky, under-powered little glorified VW. What I landed on has been a terrible investment, but it has kept me sane for 20 years now. I've tinkered, pulled the engine in and out a dozen or more times, built multiple engines, exhausts, dry-sump tanks, etc. I've had 3 sets of SEATS in the silly thing, for crying out loud. I keep changing the car to better suit me as I move through middle age.
I'd have done none of that with an original. Hot rodding an original at this point would be like "improving" the Mona Lisa. It's just bad for business. But I don't want one more thing with a set of rules to follow. I want to color outside the lines.
The OP might think he wants an original, but the very fact that he's here with the great unwashed betrays the fact that he doesn't, really.
My advice has never changed. If something else will satisfy the craving - then a guy should buy that thing, post haste. If this itch can be scratched with a Mustang, Miata, MG, or Maybach, then by all means - BUY IT NOW.
But if you are like the rest of us misfits, who want something that is ours (in every sense of the word) and who cannot sleep without dreaming of a 356 speedster that will never rust, always satisfy, and be customized just for you - then there's absolutely no saving you from yourself.
May God help you as you incinerate time and money on a fool's errand. Come. Join us in our folly.
Welcome to the Madness.