For the bumper bodies, i sanded off the art, as the plastic on these bumper bodies didn't like the thinners

as it turned out, two of the bodies were cracked anyway, so i found some old Gtb ones and used them instead, as they are essentially the same.
Anyway i sanded off the art, placing some 320 grit sandpaper on a flat surface and rubbing the bumper body across the sandpaper to remove the art. I finished off using 800 grit to ensure a nice smooth surface for the decals. 1st pic shows the bumper bodies after sanding.

And the second pic shows the end result, with the decals applied and after a couple of coats of clear. should look quite presentable i think!