I wanted to add a bit here. First off most of the major points have been covered.
Biggest thing with VW's is that parts quality are all over the place. Plus they change in quality over time and even between suppliers. Guys that make good heads get bad batches of springs and never hear back so they continue building with the stock they have. Electrical parts are 50$ German made relays to 8$ universal parts that may only survive for 3 months in daily use, but on a weekend driver make it years. So building full cars is a crap shoot. I use OEM parts as much as possible from old beetles because they are built to a higher quality then almost anything out there.
As an example I recently got a new endplate axle cover set where the difference in the bearing mount surface was almost 8 thousandths out. At 50$ you ind of expect that. Same thing with seals. Right now I spend a lot of money when building on sourcing super high quality seals. (You said you have leak) I also flatten and glass 2000 grit sand all seating surfaces when it makes sense. Almost every single VW seal that you get in a kit from the big suppliers is garbage you will have leaks.
I have had a few vintage speedsters and maybe I have been lucky but I have used mine as daily drivers and put ~6-7K miles a year on them when I had them and mine were pretty much as reliable as any super beetle. But I had 1600/1776 motors with minimal modifications. The 2276 that I have in my 550 Spyder at almost 11:1 compression yeah that is not going to last or behave the same way.
Also price is a thing. I have no idea how some of these guys build cars and sell them at the price they do. A properly build 2276 like mine built by somebody like ace would run 10-12K depending on options, another 2K for a good transmission. I would charge close to 8K to build say a dual carb 1776 drive-train complete with good cores.
Big thing is a car like that with the leaks you have could be fixed very cheaply by yourself and the pricing you have is out of control.