So this year I want to park my (hopefully done) '75 2.0l at Hershey with a big fat FOR SALE sign on it(-worth it?) who do I need to talk to or where do I go to reserve a spot? Question number two: is it worth bring the car down for sale? Are there buyers at hershey?

Thank in advance!

I will be making a list for vendor spots.

My opinion - I parked my car in my vendor spot and had many people ask if it was for sale and how much? It wasn't for sale.
There is a car for sale area at hershey but if you park the car there you will feel obligated to stay with the car to answer questions. I looked around the area briefly but didn't spend any time there.
I would park the car in a vendor spot along with the rest of the 914 crowd, hang out, have a good time, get exposure and either sell it or at least pick up a lot of exposure. If it doesn't sell, you still had a good day.

Do you mean Hershey in April for Porsches only ? or October for antiques ?

April.