Those hold 17,670 pounds each, so one bolt ought to do it
Eight will hold 141,360 pounds, so you are good for a van with a bit of a safety factour
:beer:
That might be what the paper says, but they'd have to prove it to me. I've had a 140,000# chunk of steel in my shop, so I know what that looks like, and I'd never trust it to a handful of 1/2" bolts, grade 8 or no.