Dan,
What ratio steering box are you planning on using and is it power? If you are going to us a Delfi 600 box like DSE offers you will not need the short arms and yes they do cost more that they should.
If the ratio is in the 12:1 or 13:1 range the short arms my make the steering ratio a little faster than what you may want. The short steering arms and the longer pitman arm was a cheap way for GM to speed up the steering without changing box.