If you have a trailer, then here is what I would suggest.Get you a small winch and pull them in to the trailer.A small 1500lb Warn will run you about the same money, and it is far easier on the back.Drop you a ramp out the back,hook the winch in the front of the trailer, and pull stuff into the trailer.No lifting,no dragging rounds up to the rear of the truck to use the crane,no reshifting the truck around.Run the cable out to the round,drop a loop,and hit the button.
I can load my sixteen foot trailer slam full of wood in less than thirty minutes of large rounds and drag home 2 full cords of wood in this fashion, and dont even break a sweat over it.I often drop a loop over four or five rounds at a time, and it takes no time to load a trailer with a winch.
If you have a partner,even easier.As soon as you drop the loop your pardner hits the button.Shoot, when pulling stuff up a steep hillside I often drag the wife along.I go down the hill,loop the cable, and ride the stinkin log right back up the hill as she holds the button down.
Cranes have their place,but mounted right in the middle of the bed I think is going to cause you grief and more work than its worth.If you have to dismount the trailer, hook the crane up,load the wood, and rehook a loaded trailer up I think you are going to be wore out from all the effort and will be discouraged from how much you put into it and what you got out of it.The only other option that might work is mount the crane right in the bed of the trailer if you have a sturdy floor and frame under it.