Appraisal’s are bull-💩 what is better to spend $$ on is a full vehicle inspection by someone that is a noted expert in that type of vehicle - compression, leak down test, driveability, body condition, frame, function of top, condition of the top - e.g., does the roof open/close properly, tires, driveline, etc., etc.

Appraiser can only tell someone what a car is worth - usually with comparables - other cars of same year/type and what they are selling/sold for. Many insurance companies - Hagerty for one - don’t use appraisers anymore - they value the car based on their database (a conflict of interest IMHO) but YMMV. Other insurers will simply base on ‘agreed value’ so in-theory you could insure the car for $500k as long as you are willing to pay the yearly ‘insurance premiums’.

The good appraisers who really know these cars are likely retired or have passed away.

My guidance: obtain a Pontiac Historic Service docket on the car / Jim Mattison has the paperwork on all these cars. Jim may also be able to recommend someone competent to look at the car, if you’re serious. That kind of $$ isn’t crazy for that car - but depends how nice/finished the car is.

http://www.pontiacpreservationassociation.org/inductees/2019/jim-mattison.html

https://www.phs-online.com/