Maybe it would be a lot easier to swap a 3.8 or 4.2 V-6 in there to replace the 2.8?
Won't get the brute force of a 350 without some work (maybe turbo a la Grand National or blower a la Regal GS or Pontiac GTP)
Of course, add a lot of power/torque and the rear end needs upgrade, but at least you have less weight on the nose...