disassembled is "best" as you can be completely sure of getting it cleaned and painted/powder coated. Sand blasting is not recommended; its too coarse. Glass bead is better, but only if motor is completely disassembled and then THOROUGHLY rinsed/purged of media afterwards. Vapor Blasting/Wet Blasting is a highly desirable process, and it leaves a "peened" finish. You can choose any method to strip the cases to raw aluminum, but they are cast pieces. So to "polish" them is some work (vapor blast is great finish for this). You can then clear coat, or powder coat clear and leave them. Theres a thread from a member, Noblehops in "Services Offered" where he displays this process and before/after results.