Install a stop 6'' down. You could come up from below and bolt through the bottom. This is the 'blind' hole method, not seen from any angle.
or
A 51 has slanted upper bed rails. Place your metal stake and weld a small flat plate the same angle as the rail. Drill a 5/16'' or 3/8''hole and bolt in situ.
or
Drill a hole in the verticle stake pocket, about 3-4'' down and place a 3-3.5'' bolt through the wider portion of the pocket.


Jim & Caroline
The highway is for gamblers, better use your good sense."
Gooday-that's my 1¢ answer due to the lousy economy ~ cause I ain't got - no . mo . doe

Every Shaver | Now Can Snore | Six More Minutes | Than Before ... | Half A Pound for Half a Dollar | Spread On Thin | Above the Collar || BURMA-SHAVE