3awg is an odd size, you'll end up paying a ton for it probably. More common ones to look at: 1, 2 or 4awg
Most of the smittybuilt ones I've seen are 4 gauge, but even that is cheap wire, the copper core is equivalent to a quality 6awg cable, but I've yet to see anyone burn the cables up (unlike the winches unfortunately)
My superwinch 9500 had 2awg leads. It had an integrated selonoid but I relocated it because I custom built my bumper and wanted the feet forward on the winch, which lead to interference problems with the selonoid and the sway bar disconnect motor when I had it rotated up. I put the solenoid next to the battery, and ran 2awg cables for everything down to the winch.