I have a 2002 Deville w/standard brakes. Can I convert the front brakes to the HD J55's? If so, what parts are required?

Almost anything can be done if you throw enough money at it. You will need a J55 limo/hearse to get all the parts needed - brake parts, axles, suspension, wiring & computer, wheels (6 lug), along with any other misc stuff to complete swap. Not all limos and hearses have J55 brake option.