Some of the scratches and casting marks are pretty deep. Most of that wont come out with just a light sanding. If they were going on my truck i would almost start from scratch with 220 grit and go through all the way to 2500 grit. Thats a lot of work, but i wouldnt be happy with anything else.
If you just hit them with 1000 grit wet and move to 1500-wet, 2000-wet, 2500-wet, and then hit with mother polish they will probably look pretty good. Like I said, i can do them for you if you want, might take some time to get done, but they will look pretty hot when i'm done.