[Ikera]

Thanks for the input, well I couldn't get an answer so I just went a head and starting wiring stuff.

I connected the Tach, Door Open, dome light, Neutral switch to the gauge cluster harness behind the gauge cluster.

Actually there is no neutral switch wire there, but I didn't want to run a wire across to the other side. I'm just too lazy for that so I connected the neutral safty switch wire to the parking brake light on the gauge cluster harness.
Door open and Dome Light connected together to the door open light also on the gauge cluster harness.

Everything works fine, remote start, door open alarm and all that good stuff.

I know 240sx have 2 starter wires, one for the starter and the other is for ECU at start however in my case the car starts just fine even when the second start wires is completely cut off