And I have a pair of the C7 uprights that have been "molested"-- BUT IN A GOOD WAY. The upper ball joints have been pressed-out and a sleeve inserted. This lets you choose an extended ball joint to work camber change. The lowers have been reamed for 6141 ball joints - a more common BJ from circle track racing.
If you are planning on using the "stock" GM upper and lower control arms - forget about these.
But--if you are thinking of designing your own, they could be very useful. They still take the GM/SKF bearing. The C7 uprights are much lighter than the earlier C5/6 uprights, GM learned a lot about strength to weight and changed their castings. This image is not of mine - but representative. [Only registered and activated users can see links. Click Here To Register...]
I'm going to full race mode and my suspension is now all rod ends.
I would let these go for less than what they cost from GM Parts Direct (they had the best price) and no charge for the machining. In fact I'd make a deal for Black Friday too! (need to get them off my shelf!)
Sounds like a real cool project. Look forward to seeing the plan/layout and pictures of the build too!
Cheers - Jim