First make sure you have virtually pit free arms. 2nd make sure they aren't all gouged up from pickle fork removal . 3rd make sure they aren't cracked . I prefer to have arms that still have original riveted ball joints. makes for a much better job - If they uses a torch or a air zip gun to take out the rivets, you will always be able to tell. If someone wants me to get rust pitted arms I usually tell them not to send them without them get them glass beaded to check out the pitting. It gets to a point to get the pits out its not worth the time and effort when I can get rust free cores. By the time you grind out all the pits you lose the original metal stamping and strength and the labor will add up to more than buying better cores