If it is a good powder coating, it will have to be stripped in the sand blaster. I have worked in the powder coating shop onboard the U.S.S. Abraham Lincoln and have quite a bit of experience. You can get away with it if you bumper is flawless but results are not guaranteed. we have done it before on harley davidson exhaust (for my buddy) and it didn't turn out great. the powder just looked super dull. However I do have an Uncle that has a new machine that actually uses paint instead of powder and comes out beautiful. It can take quite a beating too, the process he uses makes the paint strong like powdercoat and quite a bit cheaper. If you are interested e-mail me and I will see if I can get him to hook you up!