340 is gutted

If that's the standard rock guard type coating, the sandblaster may not touch it since it's a rubberized type of material. A small air grinder with a grinding disk, or an electric sander with a coarse disk, will usually get most of it off, then you can DA the rest off with a 24 grit disk. Been there, done that, and I don't envy you at all. Good luck.