Hi Connie,
PCA has compiled a list on their national site of organizations that offer Porsche valuations (for insurance purposes):
https://www.pca.org/porsche-valuesExcellence Magazine also has a "Buyer's Guide" that can be accessed digitally for $4.95:
https://www.excellence-mag.com/resources/buyers-guideValuations depend greatly upon condition of the vehicle, so an "in-person" examination of the car might be essential to determining a value. There are a few folks in the club locally who are involved in buying/selling/collecting vintage Porsches, so they might chime in here to offer you advice. Before any transaction on a vintage car, a PPI (Pre-purchase Inspection) is usually necessary to establish condition. You might have a local shop like Black Forest inspect the car to help you determine what condition it would be considered to be in by a potential buyer.
HTH,
TT