There is one spacer - on the passenger side. It limits the total movement of the rack. After that all the movement is relative.
I need to correct myself. I just found a picture of the passenger side of my rack and I did use a hose clamp to hold the extension! The picture is taken from above and behind the front suspension. Don't be confused by how my frame looks different. I have an early Spyder frame which gave extra access (on both sides) to the steering U-joint.
The spacer is just a piece of tubing that fits over the rack itself. Unfortunately, I can't give the length but once you find that, it should be easy enough to fabricate. You could make it out of a piece of mild steel tube or pipe. You might check a parts supplier (r.d. enterprises, Dave Bean Engineering, Lotus Supplies, SJ Sportscars, etc. They might be able to give you some dimensions if they don't have the part.
The holes really threw me! I have heard of people boxing in their A-arms. They are designed to absorb energy in an accident so less energy is transfered to the frame (hopefully saving it from damage). The reality is that they are becoming pretty rare and if the time hasn't come yet, it probably will soon when you will have to go to aftermarket tubular A-arms. It looks like your DPO went for a sort of "partial" box job. I decided to keep the stock lower A-arms (thinking they would be the most likely to be involved in a problem) and got adjustable tubular upper A-arms.
As for what you're doing, I think it would be great to share that. It might give others a new idea. Some of us just like to see what others are thinking!