For guys whose backs or legs hurt when gutting on the ground you might want to try what I do as more often than not I am alone in the woods. .
I keep a sheet of plywood in the bed of the truck and pull it out to make a ramp. Tie a rope around the deer head and run the end of the rope through one of the front cleats near the cabin. Grab the deer , or rope near the deer, and pull the deer up onto the plywood - doesn't have to be all the way, using the tension on the rope to keep the deer in place. Cinch the rope on the cleat and the deer will now be secured on the "ramp". You have a lot of leverage and it is easy. It is then very easy to then pick up the plywood with the deer laying on it and slide it forward into the tailgate.
To gut it, turn the deer sideways and tie up the up side legs to the upper cleats in the rear if you have them. This keeps the belly exposed, easily accessible without bending, and the deer from flopping like it does when on the ground or not secured. Finish gutting and let everything slip right off the tarp on to the ground. You can then throw a bag of ice into the deer chest cavity if inclined, wrap the tarp and drive off to the processor.
MUCH MUCH easier on the back and legs.
A rare trick I got to teach my dad.
