I have QA1 single adjustable on the Panetra and double on the GT40, I wanted the extra flexibility on the latter as it handled terribly with the Spax when I got it, but honestly in 15 years of ownership of the Pantera I have only corner weighted and adjusted the settings once, so I don't think there's a lot of advantage to the double adjustable on a street car.
The double adjustable QA1 part numbers are DD501 (bushing) or DD502 (Poly), single adjustable DS501 and DS502 respectively. The bushed shocks will require a spacer either side of the eye and most aftermarket shocks will have a 1/2" dia eye, not a 12 mm (0.471") Pantera shock bolt dia.) so there is a slight mismatch that the stepped spacers take up. I can send a drawing if you go that route and need to get the spacers made up. You can of course drill out the shock mounts and use a 1/2" dia bolt. I am running 550/450# spring rates on the GT5 in 12" length and would opt for 450/350 initially on the L when I get to it. Springs are $65 ea so not terrible cost if you want to play around with a couple spring rates. The GT5 fronts are set at their lowest height so I could probably get a way with a 10" spring and little bit more preload.