Was thinking about buying a used Jaguar XJL supercharger from a parts car. Would this be worth it or should I just take it to a performance shop and have them throw a whipple on there?

 

Short answer: NO.
Longer answer: This question has been asked a bazillion times before and the answer has always been the same - it could possibly be done but not without yuge expense, way more than simply buying an already supercharged car, and no-one has ever successfully done it anyway. Too many differences between the NA and SC versions of the AJ133 and the electronics/wiring/modules/programming etc etc etc, you would need to replace almost the entire wiring harness and most of the modules in the car.

 

+1 on OzFXR's comments.

Additionally, the lubrication system is different for the supercharged engines to control piston temperature.