Try to find your original build sheet, places to look 1) top of gas tank 2) under carpet driver side 3) under rear seat. If you don't have one you can try to retrieve a build sheet from Pontiac or use several services that can provide you with an original build sheet and even the window sticker; http://www.phs-online.com/services.htm - or - http://www.gtoalley.com/ FYI only "the Judge" came with the rear spoiler AFAIK, but maybe some more goat-knowledgeable members can say for certain.
I think that a spoiler was only offered on the 69 Judge models. As for the hood tach, it was typical for the period on all GTO's but I do not know if it was an option or standard. As KenF said, unless you can find a build sheet (unlikely after 46 years) or pry info out of Pontiac archives, you may never know how your car was optioned from the factory.
Tach, yes. Not sure about the spoiler. Contact Allied Vaughn. For $50.00 you can get a copy of your car's original factory to dealer invoice if your vehicle identification number is available. That'll show you what options your car had when it left the factory. Google "gm media archives" to get to Allied Vaughn's website. Some options, such as the tach and spoiler could have been dealer installed options as well. HTH. -Jim
Looking for a Used GTO in your area?
CarGurus has 432 nationwide GTO listings starting at $5,995.
Search Pontiac GTO Questions
Pontiac GTO Experts