This should be a straight forward swap if you can find a V8 car in a yard. You'll want to get the trans xmember and the frame towers for the engine mounts. Of course you could build your own xmember if you are so eqiupped.
Being that the Malibu is an A body and the GN is a G body I am not sure what the difference will be in the rear end suspension points.
A custom drive shaft will be needed and you may want to upgrade to a HD V8 radiator and shroud.
Mark