My friends that own (boundy little archaic and ride worse than a Karmann Ghia) 356's would tell you that is a $7500 car.
I can tell you for a fact and show receipts that to remove and replace the Dilivar studs, exhaust valve guides etc. all things that a "top end" build would require plus the "may as well since you are there" things such as a clutch/pressure plate/throw out bearing WILL run you at least $10k....... 5 years ago.
Any SC that still has Divilar studs are going to go - it's a matter of time, especially the exhaust side (from the heat and the elements).
That's the only place you will find the Dilivar head studs on an SC is the bottom row on the exhaust side. The upper row are steel.