Upper and lower torque box reinforcement kits are available, as well as an upper mount that completely replaces the stock mounts.
The stock upper mounts are actually spot welded to a heavier metal 'crossmember' that reinforces the floor pan and provides a secure rear seatbelt anchor point in this area. This is what you really weld the mounts to, not really the actual floor pan.
This car will be a street/strip car, not a weekly bracket car, so I really don't think I will ever have an issue with them. If I were beating on it week-in and week-out, I would certainly pop for the box reinforcements.