Do any of you own an original Porsche Speedster or an Intermeccanica Porsche Speedster replica?
I own an Intermeccanica, and mine's a Vancouver tube-framed car with roll-up windows. My car is nice, but it's fundamentally no different than anybody else's replica. It's a beautiful car with VW running gear. It's a nicer purse made from the same sow's ear.
Intermeccanica builds a really nice replica, but it isn't (and will never be) a Porsche, or even anything very special to anybody outside of a very few people who dig pretty deeply into this hobby. I know you are hung up on this, but the company that built your car is pretty much irrelevant.
At any rate, at this point I can pretty much guarantee that the engine in your car is not the engine put back there 45 years ago. And here's something else to chew on-- for at least 25 years, Intermeccanica has used engines from CB Performance for Type 1 Speedsters and Convertible Ds, so there isn't anything unique or special about the engine in one of their newer cars either.
It's a popular sport in service businesses to tell people that the last people who worked on anything (your electric panel, your furnace, or your car) were idiots who didn't know their backsides from a hole in the ground. Sometimes that is true. Sometimes it is not.
I would never take a Speedster replica (of any make) or any air-cooled Porsche to a Porsche dealer, because Porsche dealer service departments are equipped and trained to work on Porsche models in (or just out of) warranty. They're not equipped, trained, or experienced in any vehicle for which there is no longer factory support-- which is to say, no vehicle older than about the 10 most recent model years.
It's the same at a Mercedes, or Volkswagen, or Honda, or Toyota, or Ford dealership. At some point, independent shops take over, and at some point after that, it's straight-up vintage enthusiasts and a smattering of shops catering to the various hobbies.
I wouldn't take a modified '32 Ford with a 351 Windsor to a Ford dealer and expect decent service. I wouldn't take a '69 Camaro with a blown small-block to a Chevy store and expect they would know what they were doing.
The Porsche mechanic may know less than the guy who changed your clutch. Your engine may indeed be ruined-- but it may not be. It's super-hard to see what the problem is from your pictures.
I know what it is like to feel like there aren't any people in your city or area or time-zone who know what they are doing. I felt like that for a long time as well. But after going it pretty much alone for 15+ years, I began to figure out that there were other people in my part of the world who knew a lot about air-cooled cars.
I can guarantee it's the same in Australia.