i dont think 09 head pipes will work on a 08 cuz of the lower cross over bolts to the oil pan. i may be wrong and iam sure someone will chime in here shortly. plus the 08 head pipe comes off the rear head and goes left and down . the 09 goes under the frame.
Will the 09+ Street Glide Exhaust setup fit and 08SG or will it require modifications?
Thanks,
VBouncer
It can be done , but requires modifications and replacement parts. There has been a thread posted by a rider that did this exact thing on his '08.
The frame changed in '09 making the rear wheel 1" back from the motor sub assembly. This was to make room for the exhaust cross under the frame. To mount this to the '08 and earlier, you will need to replace the oil pan and associated parts with '09 and later. This has the mounting points for the pipe supports. (Or you can modify your original pan) The pipe will need to be shortened the 1" to fit also.