In my humble opinion , it depends on your car as it is now. If its close to'original' and you can keep it that way it prob. will be more valuable in the future, but if its 'bastardized' as mine was when I got it( I still try to do it mostly original ), I`d just 'go for it' , make it fun for you! Add all your options as you like. Mine was a 350 car , midnight green w/ dk green it and top, it was lt blue for awhile before made red w/ black deluxe interior ,I have added 400 hood , since former owner added 400 engine. I have added 70`s T/A exh tail pipes, a dash clock , under hood chrome (valve covers, air filter cover,brake fluid cover and so on).the car has chevy SS rims , nor rallye II`s , aftermarket tach and wood steering wheel.
Most people that see the car have no idea , but any " Firebird nut " will. It turns heads everywhere and is fun to drive , it does what I want out of it. What do you want out of yours? Have fun today! Nobody promised a tomorrow, Bjorn