The alternator on my big rig won't run a 12k winch at idle, or anywhere else for that matter.
As an example, big rigs will normally run @140 amp alt. but have 4 batteries with 1000cca each. See the point I am making?
The winch uses battery power. The alternator just keeps the battery topped off.
A high quality battery and a regular alternator will do just fine, I have never replaced an alternator due to winching but always run a quality battery.
If you want a higher output alternator, then fine, but never expect it to run a winch.
1998 XJ on 37's.JK Rubi axles with chromo shafts and ctm's, 4:1 transfer case, etc etc etc.
2003 Range Rover HSE, 4.4 Quad Cam.
1998 Range Rover with a 6.0 LSx
1994 YJ, 4.3/700R4/OME SOA, etc
Western Star 4900EX 4 axle.
4.3/700r4/new frame buildup (YJ)....