Thanks for your comments. The percent of stiffness the connectors add is an unknown to me too. I put solid subframe mounts on my camaro and have autocrossed it with some success. Before doing that, I could feel the sub move separately from the body by feeling the gas pedal move when I hit bumps!
I still don't have the connectors in my car but plan on adding them.
I think the biggest improvement is in the solid sub bushings. The connectors have to add something, but exactly what I don't know.
If I can I will try to measure the torsional stiffness change on my 67.
I have seen a lot of first gen Camaros vintage racing without the connectors. Even the Penske Camaros didn't have them.
I'm not saying this is right, but I believe the rules didn't allow it.
I was suprised a bit by Herb Adams answer but it reflects my hunch that the connectors are not the first thing to think about when improving a Camaro.
I have recieved comments from others that they are a BIG improvement. I just have some doubts and need to prove it to myself before going along with the crowd on it.
I'd like to hear from someone who did just the connectors alone, but HAS done the solid sub bushings.
Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer