I don't think it would just "work" , without several
hundred hours of fabrication.
Their is a 2000-2002 Grand Am that's rear wheel drive, and I think it has an LS motor. Thier's a link around here somewhere, think it's up on CarDomain.....
A newer Grand Am with RWD and a V8....that would be nice !!
I dont even think the Eldorado trans would even bolt to the NS...
But you would need to measure the subframe on the NorthStar and see how much bigger it is then the GA subframe then figure out how to engineer everything to make it work.
Good Luck and take pics !!