Custom manifolds are very tricky to do as they contain a water jacket and the thermostat.
I don't think that playing with the mixture screw is the answer to your problems.
Steve (http://www.risingsuncarservice.com.au/) from the Ausubaru message board has done it.
Wiring harness is a piece of piss! How hard is plugging in a dozen or so wires?!?
You actually might find a N/A EJ22 to be a better swap. With the EA82 or DOHC EJ swap you need to cut into the chassis rails as the engine is physically to wide.
To determine which winch, multiply the weight of your vehicle by 1.5. I use a Warn M8000 Low-mount on my 1987 GL Sedan, which is a little bit too much but I'd prefer too much than not enough.
You should use a dual battery setup too.
You really should try www.ausubaru.com dude.
Under $4K for a crappy one and up to $6K for a really good example, but don't pay more than $6K. I picked up an unregistered one with a blown engine for $1,500 a few years back.