When I installed the winch on my YJ I set it up for a dual battery system. The Jeep doesn't have A/C and is the 4cyl.
I found an old style Motorcraft alternator with the external regulator. Fabbed a mount to locate it in the A/C spot. Fabbed a shield to go around the fins on the alternator. Got the proper pulley for it.
The reason for the external regulator is that I can disconnect the alternator from the battery, put on full 12V to the field and get 120VDC out of it to run any brush type 120VAC tool.
I found that 2 of the small batteries will fit (SNUGLY) in the battery case. Don't remember exact type but have posts on top. The 2nd battery was then run to the winch.
Also, I put a solenoid between the two batteries with a momentary switch under the dash. That way, IF I left the lights on, battery was dead, or in Minnesota winter, I could push the momentary switch and bring in the 2nd battery for starting.
When I abandoned it in Minnesota 4 years ago I switched back to 1 battery and left the 2nd alternator installed. Now that I am restoring the Jeep, I will set it all up again.
You can get an electronic regulator for the Motorcraft alternator as they are extremely common.