Replace 1 bushing, or everything?

Ok, here's a question. I've got a 73 car with the 73+ disc brake setup, but a 70-72 k-frame. Is the 73+ sway bar different from the pre-73? Are the bushings between the k-frame and sway bar different for different years? I know the end links are different, but didn't know about the middle bushings or the bar itself. If so, how do I tell which sway bar I have?