I didn't see a thread on this, so I figured I'd throw out my solution. I just fit my Charger 220 exhaust on my P220, and wanted to retain the spare tire in its current location. Obviously, the left hand pipe prohibits the spare tire's space.
I solved it by buying a bunch of the M8x1.25 pitch spacer nuts that are used for the cylinder head's attaching to the cylinder shroud. I also bought some m8x25mm bolts to screw the spare onto the spacers. I threaded the spacer nuts all the way on the upper spare studs. I took a m8x25mm bolt and threaded it in backwards through the bottom spare tire captive nut. I then threaded a m8 spacer onto that bolt.
Mounted up clean and easy. When I mounted the spare, I did it with the wide side out, unlike when its normally fitted. Fits under the cowl without any problem and looks just like stock.