I have two buick 3800s and they take 5quarts (4.7L) with a filter.
To find out how much oil it would take to damage it you'd likely need to contact the GM engineering department.
The problem is when you get too much oil the crankshaft starts to whip the oil into a foamy mess and the oil pump starts pumping (trying to) the foamy mess with a lot of air bubbles in it. The air doesn't support the rotating assembly and the bearings start to get scored and eventually fail. The cam bearings, connecting rod and mains would take the worst of it.
95 Regal 3.8 130K
97 LeSabre 3.8, recent intake, 200K
The advise is free, you get what you pay for !!