Anything that is cast, will not anodize nice. anything that has been welded will have a slightly different color at the weld. Different alloys will also have different shades. We use P.K. Selective. If the material is a good clean alloy like 6061 t-6 or 7075, than it is unbeatable. Castings should always be polished. Powdercoating is just a thick paint job. there are some applications that powdercoating is good for, like covering old parts that just wont clean up. I may have spoken to you on the phone, and if you would like to come by, we can steer you down the right road so that you waste any more money. Engine parts that are aluminum should never be coated or chromed. they need to breath, to cool and disapate. Joe