89 GT ground effects

if you do as Speedytang says, make sure they do have flex agent in the paint, or you will likely crack the paint off while mounting (if the FX flex while trying to get them on).

good luck.
 
As far as blasting goes if you do use a VERY soft material. And as for painting them I've done it both ways and the only thing about painting them off the car is the reinstall even with the flex agent they want to crack and it's real easy to scratch the paint on the fenders. My suggestion is to paint them on the car.