If you are looking for Impala specific problems, you should be on an Impala forum rather than a general car forum. I don’t know of one but there seem to be forums specific to darn near every type of car.
Take a closer look a the pictures of the rack online. Bushing… not bushings. Just one. The rack has one solid mount and one bushing mount. If the rack is moving around at all, the rack’s casting may be cracked or the rack’s mounting bracket may be cracked.
As for replacing the rack yourself… I think the engine cradle needs to be loosened all around and lowered quite a bit at the back to get the rack out. I don’t think the rack can be removed with the cradle in place.
You will need lots of jack-stands, a floor jack, maybe an engine hoist, and prayers that the cradle bolts haven’t rust-welded themselves to the car body.
Try lubricating the sway bar bushings or replacing them. Sway bar bushing creaks can be common when age affects them. You may be able to replicate the noise by pushing down hard on each front corner of the car.
Another less likely cause could be the coil spring pads on the front struts.
I went ahead and replaced the rack and pinion myself this weekend and it fixed my issues.
Thanks to everyone who gave insight and actual suggestions! I appreciate it!
The subframe only needs to be lowered in the back of the engine, and it was very easy to do. The toughest part of the job is getting the fluid lines off and on since they’re in a very hard to reach spot. Lots of extensions, a swivel socket, and a crow foot socket.