1-3 are region, country and manufacturer. 4-8 are model specific digits.
The 4th digit is the vehicle category. 'G' indicates multiple cylinder sport street.
The 5th digit is the piston displacement. And 'D' would indicate 80—89cc!!! Should be 'N' for 500-599cc. Or 'R' for 700—749cc.
Like you said, 'T' is for the 1000, or 850—999cc.
10th digit is the year, and
should be Y for 2000.
I don't know what you've got there... Maybe certain replacement frames that fit multilple years are labeled differently? I don't know yet, but I will keep checking.
Have fun with it. Check out this site for Suzuki specific VIN info. >>>
http://www.suzukicycles.org/_misc/identification.shtml