A) Depends on what you're going to add. A good battery is key, and use relays for anything extra installed. If you're talking a pair of Hella 500's, you'll be cool. If you're talking about using a 10k worm electric winch all day long, you'll want a dual battery setup and an upgraded alternator. Build to suit.
B) Select your winch by use. If you're going to not use it and want it on the front of your Series to look cool, pick what you like. If you want it to be period, a capstan would be fine; as would a PTO (such as a Koenig); but a Warn 8274 would be fine too.
If you're going to *use* the winch, then think about it more. Do you want to sit in one location and winch lots of vehicles out of a hole, I'd suggest a PTO winch. If you want to use it for self-recovery, I would prefer an electric.
Pros/Cons of each: an electric can smoke your electrical system, may need cooling occasionally, but it can run w/o the engine off. A PTO can be run all day long, but is more mechanically complex and won't work if you can't get the vehicle started (ie, bogged in a waterhole, or on its side). If you were going to be sledding logs around, a capstan might be ideal, but isn't as friendly for recovery.
FWIW, I've got a Koenig, but it is an electric instead of a PTO version.
-L
'72 SIII SW 88"
'60 SII 88" RHD