That is probably at the crank. J+S Machine did an Edelbrock aluminum head 403 with 3.5" stroker 421 ci, over 500 hp and well over 500 ft/lbs, want to say 550 ft/lb of torque at the crank. There is your 475 RWTQ number right there.
Respectfully, not a chance. I will eat my words when I see evidence that doesn’t include nitrous or a turbo. A Buick 455 was an anomaly with 510tq and even it had a 3.90” ‘short’ stroke.