i don't know about a 70 but a friend of mine and i put a front 60 in his truck and when him and i picked it up the veins were poping out of both of our forheads.
i'm going to guess between 450 and 500 pounds.  just cause i know i'm good for 250 dead lift from the floor and being odd shaped brings my limit down.  

(hey i wander why i just had a hernia repair operation )