You say you spoke with SPC. Was that the company or Mark (Savitske)?
If the company, I suggest you give Mark a call. Make sure you have some time to talk - it might not be a quick answer. He is very knowledgeable. He can also give you some alignment hints too.
His page is: [Only registered and activated users can see links. ]
Phone not listed on site (610-346-8154).
Get a copy of his book - How to Make Your Muscle Car Handle.
Cheers - Jim
I'd go bone jarring Delrin personally. The set I got from Mark are 3/4" shafts with thread in ball joints. Setting up to race (since 2009!)