Weld-in subframe connectors and torque box reinforcement should be enough to keep it together. Though I will say with 600hp / 550tq, you'll be looking into the 9s which requires a whole new set of safety rules. You'll need a 10-point cage certified to 8.50 with sticker, IHRA/NHRA license, SFI certified balancer and flexplate/flywheel, window net, engine diaper, full protective clothing to include jacket, pants, shoes, gloves, helmet, and neck collar, aftermarket axles with C-clip eliminators, SFI bellhousing, harness, and a parachute if you exceed 150mph. (doubtful unless you're putting this in a dragster)
That 10-point cage would handle your rigidity needs plus the other safety requirements to keep the car together and you safe. It's something that you need to consider when building a drag car. Once you dip under that 9.99 ET, the cost to play goes way up.
BTW, what's your plan for the build to make those numbers. Considering the high torque number, I'm guessing either a big cube 408-460ci windsor with a lot of compression or a 351-408ci engine with something like an underdriven 6-71 blower. (which would look badass)
EDIT: Not trying to discourage you with that but just being realistic. If you go to any decent track and run a 9.99 or quicker (or 135mph or faster) without the necessary safety equipment, they'll usually give you a warning the first time and 2nd time give you the boot. You'll need at least a 6-point rollbar for 11.50 - 10.00 cert anyway. Just recommending that keeping your power level down a tad to around 525-550hp may allow you to keep from shelling out thousands in safety equipment, be able to abuse it at the track still being quicker than the majority of the people there on a fun run night, and still have more power than you can put to the ground on the street.