I have installed 4 harbor freight winches on concrete floors over the last 10 years. They are all working great. Many heart attacks prevented.
You can never know if you have the correct size until you install and try it though.
I bought the lowest power one and it struggled with getting a 3000lb plane over a 4" door guide, upgraded after 5 years to the next size up and much better. All four are that size.
The size depends on the weight, slope, and surface smoothness.
I will try to find the model I used.
Mine are all 120V modified with a 100' 14awg power cord to the switch (if you are 12V I wouldn't know which one to suggest)
They all have a shut off switch actuator (which you can reposition), in case the cable does not stop when you think it should. I remove their winch cable and install the length I need as typically theirs is too short. I rewire them so the power cable only requires 2 conductors and a ground wire (they come with alternative wiring).
The switches do fail, I've replaced a few now. I have also had the safety switch fail.
Edit: here is the one I've been buying, its actually a hoist.
http://www.harborfreight.com/880-lb-electric-hoist-with-remote-control-62854.html
The mount I make for it is pretty simple to make, lmk and I will spell that out.