I'm running Gen II pipes on my Gen I.
What I had to do was use the mid-pipes from the Gen I, the pipe itself fits perfectly, but the mounting holes don't line up, so I used over-sized washers with the existing bolts to hold onto the lip of the Gen I mid-pipes (makes sense when you try it.) I also fashioned a pair of small L-brackets to hold the chrome front trim. Lastly, I had to use a pair of $1.75 U-Bolts from Home Depot to extend the mounting hole on the bike, but I plan to make a more elegant mounting plate soon.