Elbows can mount to the manifold directly, or with a riser (which come in a few different sizes, 1-1/2", 3", 6")...
It's the engine installer's choice as to the use of a riser or not. But if you currently have 3" risers, stay with 3" risers. I also prefer the 'all in one' gaskets.
That elbow in your link is the same as the one for your engine (from the parts diagram), but just check, as there is also a 14° degree elbow. Just check your current one is the 7°, or find a casting number on the elbow somewhere.
Chris.....