i think if you wanna see if they'll devalue, it's worth looking at what the value has done thus far... a good condition, fairly original one, is worth about.... $5K... if that... originally bought from the factory, i'd bet they were atleast double that, can't be sure... but as a rule of thumb cars don't appreciate in value, only depreciate... that is unless you get one of those rocking horse shit rare cars... something that cost a mint when new... a XJ13 Jag for example... 'far as i know there's only 1 left in existence... +1 clone in perth... now that's worth a pretty penny
moral of the story... don't go spending big bucks on modding cars if you expect to make a money out of it...