I am really surprised this didn't kick up

I get what he is saying however the factory's deal of putting in torque boxes to prevent frame twist was the cheap and quick way on the assembly line for stiffening a vert, 4 speed or hemi car using an existing chassis. Too much twisting and moving will eventually result in cracking sheetmetal and popping spot welds. Remember that just like anything else, when brand new these cars were only intended to last maybe 15 years, not 50 !! The torque boxes were what the engineers needed to design to stiffen em up and what the bean counters were happy with because it was cheap. Had it been cheaper to subframe connect all the performance models on the assembly line, they would have done so.

My 67 has subframe connectors and homemade front and rear torque boxes, my sons 69 will have them too. You also have to realize that when these cars were designed they had bias ply or poly glass tires typically F78-14 tires on 14x5.5, wide pizza cutter rims and tootsie roll diameter sway bars soft rubber bushings, smaller diameter torsion bars etc

they didnt have todays performance suspension parts available for them like polyurethane bushings, huge sway bars, huge torsion bars, and certainly not today's shocks or tires. You put all that stuff on, without seriously stiffening up the frame and have a car that twists like a wet noodle with all this stuff installed and that high zoot suspension system will never work to it's full potential because it will force the chassis to flex, not the other way around with the chassis forcing the suspension to work.

For stock restoration stuff, sure do as the factory intended. If you plan on putting more power, and some serious make it handle parts in there, then you would be wise to sub frame connector it, and torque box it. Less chassis flex with a high performance suspension system is best.

Just my .02
Matt