Tough comparison, I don't like the David West one because I think Sully is a better rebounder but will never be the offensive post player West has been through most of his career.
I can't think of a really good comparison off hand. If his back is really better and he loses weight, or at least fat, and gets more muscle and explosiveness then maybe someone more like Rodney Rodgers was at his best? A tough guy down low on the boards who could step out and shoot the three but not as consistently as you'd like. Although Rodney shot in the high 40%s once but was only around 4 to 5 rebounds a game.
I guess it depends on who is around him. If we have another good rebounder on the floor with Sully his stats will go down.
He will never have the speed and explosion of a Charles Barkley so that isn't a good comparison at all.