Thanks for that Shaun however,

How do you get your speedo working if not using the Silvia speedo ? and I agree I don't need the whole silvia dash but maybe as Shoota suggested the gauges into my existing '81 round dash setup might work.

Shoota, I got them separately so I don't have the loom in the middle
From what I can research I have the 'Auto Harness' the 'E.F.I. Harness' and the 'Engine Room harness No.2' as well as the shifter with its plugs.

It looks like I need at least some of the number 1 'Engine Room Harness' and some of the 'Main Harness' (at least the plugs for the AT computer and maybe the combination gauges).

I DO have all the Looms from an EXA - that will be my next avenue - chop chop

pretty sure the only wiring you need for the auto is the wiring that tells the ecu if
its in park or reverse so it will start
and in reverse so the reversing lights come on
my ca18det auto 1200 sedan only had this and its all it needed
as for sensors you need the main ones but no sensors for the auto box
you definetly dont need the silvia dash

Was your donk already mated to the auto when you got it or have you got your CA and then sourced the auto separately?
If they came together it should be pretty straight forward. All the sensors you mention are all very important. Especially coolant temp, cam, speed sensor etc as they all control the fuel delivery and spark timing.
You can use either the dash out of the Silvia or you can get electrical replacement gauges (Autometer, etc). With a coupe dash (3 round dials) you can pretty much just plonk a 3 3/8" gauge straight in the hole. Some people like to mount them from behind for a more factory look.
If it all gets too hard there are a few places around that will do a full wiring loom for you to match the recipient vehicle.
Good luck!

Ever thought that you would take the easy way but it ended up the hard way?

Ever thought that you could do something easily but the more you did the more things that had to be done? (knock-on effect)

let me say at the outset that I am gonna finish this as an auto CA18 conversion

BUT..... I have been studying the S13 workshop manual for the electrical hookup of the auto box and it is leading me down a path that may not be well trodden.

1. Has Anyone done this before - CA18 + Auto from Silvia into 1200 Ute?
2. Do I need to use the Silvia ELECTRIC speedo and tacho and warning lights?
3. All these sensors! - fluid temp sensor, revolution sensor, speed sensor, kickdown switch, Soliniods for the shifter selector

Ok I need some plugs that fit the plugs on the auto and shifter, maybe a speedo, (how far do i go?) if no-one has them i will go try the wreckers.

Any experience on this would be appreciated. if not i will document my journey in my build thread