I doubt anyone has attempted this yet. It would require modifying the Allante which is front wheel drive to rear wheel drive since the engine and transmission you mentioned is from the new rear wheel drive Cadillacs.
Several transplants of Northstar powertrains into earlier models have been reported. All were expensive, time consuming, and not very satisfying. Anything can be done by throwing enough money and effort at it, but the Allante platform is a poor choice for any extensive fabrication exercise.