David,
Actually the SCCA T1 rules don't require any specific shock. They say something like we must use a shock that matches the original configuration, meaning no remote reservoir shocks.
Most of us do run the T1 Sachs shocks, but there are guys running Koni's and Penske's. As a note, Heinricy uses the T1 Sachs shocks, so that always seemed good enough reason for me to use them and save my money for other things, like tires.
The guys running Konis and Penskes don't seem to have any advantage over those running T1 Sachs shocks, but... I've never done back to back testing either. :cheers: