My Hitchhiker pin box has a sticker on it that says that the bolts should be torqued to 150 ft/lbs.
If you can't borrow/beg a torque wrench that will go that high I think that is about how much the adverage man can pull espacilly if you are laying in the bed under the 5W when you tighten them. Like has been said before use the front landing gear legs as a jack and go for it!
I used that method to install a new Demco pin box, having a couple of extra hands to operate the raise/lower switch makes life a lot easer. Using a drift pin makes bolt alignment holes a lot easer. Get one bolt started hand tight. Using that bolt as a pivot then SLOWLY have youe buddy raise/lower the 5W to align the other holes.
Piece of cake, just be very carefull.
Be careful