I am running this:
Bulldog Winch Trailer Winch - Synthetic Rope - Hawse Fairlead - 4,400 lbs Bulldog Winch Electric Winch BDW15020
I have it mounted in my battery cabinet on a plate. I am also using the wireless remote option for it which works really well.
I love that I don't have to play Dukes of Hazard in my car when loading it into the trailer. I put my car on the ramp, hook up the winch, and pull it in the trailer. With the winch I can load the car into my trailer by myself.
Anyhow- a 4K winch is ideal. Keep in mind you're pulling it uphill. Also I would look at synthetic rope option so it won't tear up your trailer's floor. I would make sure you get at least 4k pull so you have plenty of reserve capacity in your winch in case you damage your car and need it.
I am running a 28' Intech Icon trailer. My base cabinets are configured on the left wall so that I can keep a 4-wheeler in the trailer as well. As such, my winch is mounted in the lower cabinet on a reinforced plate. I run a pulley to angle the rope down the floor and the ramp.
Best of luck.
Chris.