How are you going to power the Hydraulics? Are you going to use a PTO off the engine? Net drum too? This is important when sizing the set up.
Usually you set the gear by free spooling the winches. So you also need brakes. So now you need a clutch on the winch. All of this is usually built in the winch, but you need to make room for everything to fit. Especially the piping/hoses.
If you look in Boats and Harbors, you can find some good leads. Locally up this way, RI Engine in Pt Judith and Pine Hill Equipment in Westport, Ma. do a lot with fishing boats and hydraulics.