How much chassis stiffening needed?

72bluNblu said
Even the factory did torque boxes on the higher horsepower cars. And they were assuming skinny little bias ply tires. Even the all season radials guys like to run will hook twice as much horsepower as the factory planned for.

Not sure of the reference Torque box, but the 4-speeds, including the 340's came with a welded plate over the front of the rear springs for extra strength. True, no hook-up, no problem. Hook-up. problem. A little spin is good for a street driven car.