Arnold couldnt bench 500lb assisted. He was asked at some point earky in his career and his answer was 380lbs. Theres no way he added 120 lbs to that total while keeping his bw the same (it even dipped after 1971). Factor in that 500lbs is clearly chosen to sound impressive (its not like he maxed out at EXACTLY 500lbs) and that columbos max was 520lb (who was notoriously strong) and with much shorter limbs and greater leverage advantages, theres no way arnold benched 500lbs, just like he never calf raised with a 1000lbs. LOL.
As for ferrigno, who knows. I heard he claimed an 800lb deadlift which i find a tad optimistic considering his stature.