I have a Powewinch 712 on a 2400 pound 19 footer on an all roller trailer and use a single line.
For yours I would suggest the 912. You might even have to go double line pull. Not because of the size of the boat, per se', but because of your pesky bunks. Along with the winch I would put glyde slicks on the bunks.
They sell them right here at a very good price. Some say there are models better than Powerwinch. All I can say is mine is on its 31st season of effortless boating - best investment I ever made.