All you need is a good rope. I dropped this buck next to a logging road so I didn't need the game cart. I was the only one at the club that Sunday evening. I tied his legs like this.

I stood on the tail gate, squatted down and grabbed the rope in the middle. Remember to lift with your legs, not your back. Once you get him up you just walk backwards to drag him into the bed. If you need to you can drag him to a hill and back your truck up to that. It will make your lifting distance shorter.