Axles and radius rods a hand file works the very best, never too much off, and if it is not in your eye, like the front cross member and spring perch, may as well leave them alone, IF they don't look like BIRD CRAP... A good sand blast pretty much stress relives things...
I powder the whole frame in Satin Black, then cap coat the outside edge of the frame from fire wall forward, with the color of my choice, and the whole front cross member and perch, as I do not want to
see the inside of the frame, only the long smooth lines of the chassis and body... I hate to have to be polishing all the time, especially the inside of the frame or the under/bottom side... Driving turns me on...