If you are doing this modification you need to be careful. There is more to it than just putting together 2 Rod Ends with some All Thread Rod and a little Lock Tite.
Take a look at this picture. You will notice that the ball ends are not the same. The OEM balls are extended and measure .710" outside to outside. The replacement NAPA part uses a standard ball which measures .438". That leaves you short .272" or just over 1/4". This is a very important 1/4".
The reason our OEM Heim balls are extended is to increase the amount of deflection or 'Misalignment' they can handle (around 55/60 degrees). The NAPA, and similar rod ends, will provide only 12-14 degrees. Though we probably don't need 60 degrees, we certainly do need more than 14 degrees.
You can add washers or spacers to get back the missing 1/4". But if the washer/spacer exceeds the diameter of the extended portion of the OEM ball, you will not increase the misalignment capabilities of the Heim joint because contact with the washers will then be the limiting factor.
If you do not provide original spacing and do it correctly, you will very likely run out of 'angle' clearance and get contact between the link and the mounting bracket, mounting bolts or sway bar.
An added issue comes into play with the 2013 Spyder. On the 2013's the link is mounted in-between 2 channel pieces with a through bolt. The OEM extended ball fits snugly in the channel. But with a standard ball you're going to get slop and the link will be free to slide back and forth on the mounting bolt inside the channel. I don't know exactly what will happen here because I have not tried it. But rest assured, it won't be good.
Again, you can add washers or spacers but it is important that they do not exceed 1/2" OD to maintain misalignment angle capabilities.
I am in the process of making 50 sets of these Heim joint links which should be ready to ship out next week. I've found a supplier that has a great product that is over twice as strong as the NAPA part (7,600 lbs. static vs. 3,200 lbs. static). Not that I think the NAPA parts are not strong enough (we don't really know how strong the OEM parts are), it's just that I want to be sure these replacement links will last.
It is my opinion that it is dynamic loading that is breaking these links, not static loading. (dynamic load capability is usually 70-80% of static load rating).
The link sets I am making will include everything needed to get the correct spacing and maintain the higher misalignment capabilities that are needed on our Spyders. I don't have an exact price yet but it will be in the range of what the Napa parts cost.