Here's one of the old shocks - a Dynamic Suspension unit made in England and branded with Shelby's name. There's not much info on these that I could find, although after speaking to the factory in the UK, they directed me to a supplier in the US who could rebuild them.
Unfortunately for us, the Penske upgrade made better sense. Installation required fabricating a bushing for the rear lower control arms, as Penske uses a 1/2" mount top and bottom, whereas Dynamic chose to use a 5/8 lower mount.
There's also a small clearance notch required for the Penske charging valve.
We still have the full set of Dynamic shocks and matching Hyperco springs if anyone wants to have a go at rebuilding them.