I think many (and some here) miss the point of a classic car (even if it is a replica). Many old cars have classic lines. The 356 bathtub has better lines than most, timeless even. The rich guys think their 356 should be as fast and luxurious as the modern Porsche or Merc. Ya 0-60 in seconds flat. Hit 100 like nobodies business.
Fact is, most of these replica 356's are faster than the originals. And disposable enough to take more risk with them. V8 horsepower in a 356 body is unrealistic - sure a few have done it.
I laugh at the guys who can't handle that a 356 is slower than the modern Porsche - they don't get it. But I agree... a faster than original 356 is fun, and desirable. Within reason! Also remember there is very little in the way of safety built into these cars.
My Subaru powered coupe gets the extra power easily. No its not a rocketship, but it will keep my attention on the mountain curves and not bog or overheat on the grades. I can over drive the relatively skinny tires on it - they will howl. ...Two nice advantages to think of... A/C is not required on an open car. Skin cancer is avoided in a coupe! Lol An air cooled VW engine can have good power too, but they can be/are more finicky. ...Yet I drove my dual carbed Karmann Ghia without worry in Las Vegas Nv. It was a faster VW.
There are reasonable guys & eccentric guys... Takes all kinds. And its fun (and maybe expensive) to have that one off original replica. Build it your way!