Welcome to the Team!
You are correct.
There are different length steering arms depending if you have manual or power steering and another for quick turn steering gear boxes. Additionally the bolt centers differ depending upon the model.
A Camaro is completely reproduced from the knob on the antenna to the wheels. Problem is those parts won't fit your car. Chevelle parts may fit depending upon the year.
Good news is Chevy made more Impalas than any other car (one in ten cars made in America was a full size car); so if you need a part there may be a few left in tn the bone yard.
Thanks for the info! Do you know where I can source one at? Been searching on eBay and google and can’t find it? Any vendors make them?