Nice looking car. You done a nice job! $20k does not seem unrealistic given what they are asking on eBay lately. If you follow the sales for the next 4 weeks you can get a better idea as to what it could be worth. Consignment could be a good idea if they already have a great track record for selling Firebirds (there are a few out there).
Good luck!
Engine Test Stand Playlist: https://www.youtube.com/playlist?list=PLwoxyUwptUcdqEb-o2ArqyiUaHW0G_C88 restoring my 1968 Firebird 400 HO convertible (Firedawg) 1965 Pontiac Catalina Safari Wagon 389 TriPower (Catwagon) 1999 JD AWS LX Lawn tractor 17hp (my daily driver) 2006 Sequoia 2017 Murano (wife's car) 202? Electric car 203? 68 Firebird /w electric engine 2007 Bayliner 175 runabout /w 3.0L Mercuiser__________________________________________________________