I just purchased a 2001 Ultra Classic and making the backpack detachable so I can put a Street Glide seat on it. Will a late model seat (08 to current) fit it?
The answer is no. Seat changed in '08 as was stated.
The way the seat mounts in front changed (tab is on the bike instead of on the seat 08+) Also, the seats are different sizes due to the 6 gallon tank that came out in '08.
When I had my 06 standard, which would have the same seat mounting as yours,I bought a used Road King Custom seat,which was similar to the Street Glide seat.If you choose either of them you'll need a filler piece to fill the gap between the nose of the seat and the bottom of your console.I had originally bought the filler piece from HD,then later on bought the longer tank console.