Depends on what your goals are for the truck. Interesting swap. I'm largely ignorant of what the power limits are on the autos; most people swap to manual transmission. I haven't ever heard of anyone extolling the virtues of the Nissan auto transmissions in S-chassis cars. I know they're heavy AF compared to the manual counterparts and for the S-chassis cars at least, kind of kill the spirit of driving a sports car IMHO. I know the manual couldn't hack it on my KA-T build and I ended up swapping to a Z32 manual transmission around 400whp/wtq FWIW.
https://www.nicoclub.com/nissan-service-manuals
You're in luck. This site hosts the factory service manuals for most nissans. I'd download anything from 1991-1994 for the 240sx and it'll have the pinouts and routing for the harnesses and an AT chapter to cover the slush box. Beyond that, I'm, not a ton of help on that transmission. Hopefully someone more experienced will chime in.
As far as question 2 goes, yes, there is a SUB harness for all of those accessories. You can get one from wiring specialties or make one of your own, it's not hugely complex.
https://www.wiringspecialties.com/s13katrha.html
Unfortunately theirs is for the manual transmission. You could modify it or try to locate one for an auto trans maybe from a junk yard? didn't really find much in a cursory check on ebay.