As far as "off the shelf", the QA1s (on a reasonably stiff setting, say 8 or 9 out of 12) are the stiffest. That said, you may want to goto a different QA1 shock than the "standard" ones used on the B-body because your range of operation (piston travel length and position) is different than stock. Only downside is this may limit how far UP you can take the car with bags.
And the "different" shocks is especially gonna apply in front if you have done the common bagged car mod of moving the shocks outside of the control arms.
I'd talk to QA1 directly on this one.