OK, stay with me here. An audi 4.2L C5 motor will bolt up to a Boxster transmission and is a proven swap. The same generation C5 RS6 bi-turbo (which does not share the same block) can be swapped into the 4.2L C5 motor with the same 4.2L C5 transmission so I assume it can be bolted onto the Boxster transmission as well. Looking on eBay these motors are around $3-4K, and have 450hp out of the box and with a chip can generate 510+hp. Of course a turbo motor is much more complex but still a very cool swap idea. Someone go do this
