no a 99 will not fit. But I do have a 2002-2003 tank that is primered and ready to paint if oyu are interested for $350 shipped. Get it painted any color you want (most good painters in the bay are will do it for $100-$150.
Any of the carburated tanks should fit your M600, anything thats from a FI bike will not. There are 2 differant types of carb'd tanks (they look slightly differant but I believe they fit the same. Hopefully some will chime in and correct me if I am mistaken. So basically any thing before 2002 except the M900ie and the S4 tank will fit and work. Oh the differance between the 2 tanks is readily noticable. You can get your whole hand into an FI tank through the cap opening.