Thanks for the suggestions.
Does anybody have experience with the bumper trays that are available from...OD Iron?
OD Iron LLC Military Vehicle Parts and Accessories
They look to be tough enough to permanently carry a 75lbs load.
I think I will strap it to the inside of the bed for now until I come up with something neat. I am thinking of a "u" shaped piece of rebar welded to the front of the bed where the block hook can snap into and then a piece of threaded stock welded to the bed to let the eye of the block slide over; and I can fasten the eye of the block with some wingnut doohickey.
Cranetruck, the winch load chart is helpful; it shows that one does indeed need a 20.000 lbs snatch block if one intends to hook the block to the load and double the winch cable back to the truck to get 2x the winching power. Also, a 20.000 lbs recovery strap is needed to attach the block to the load...
If one uses the snatch block only to re-direct the winch line around an obstacle, the 5t block is sufficient.