[mpetry]

It is very difficult to estimate a value for a 356C without having the opportunity to inspect the car in person. Prices vary widely depending on condition and a paint job on these cars, properly done with even minimal rust repair can approach 20K by the time you get all the trim put back on.

Based on what you've said (sitting for years all original etc) I would say a minimum of $20K and a high of $40K, toward the high end if it is presentable and can be started and driven. $10 more if it's a sunroof.

That's my estimate. Anybody who buys such a car is looking at $20k minimum to put it in driving condition, and probably more if extensive repairs are required.