there were 2-3 parts that my old engine had to donate..tho i don't exactly remember which ones other than the flywheel..which is about 1/4 inch less think than the 996 flywheel
a new sport clutch was required.
the motor mounts had to be shaved a bit so right-side of the intake wouldn't rub against the top-front of the engine compartment where the heat shield attaches.
the boxster's ecu has to be reprogrammed to recognize the new engine or you end up with a larger engine that has the power of a stock boxster and backfires...
new headers and cats are required...tho i ended up using my old muffler because the used dansk exhaust system i got was for an 'S' model and the mounts are different so something would have had to have been fabricated and i was impatient about waiting for that...