If your ECU has facility for an 02 sensor input, then use it.

There would be less than 10 wires that need to interface with any of your existing Datsun wiring.

I think you guys might be in over your heads.

Shouldn't be that hard for anyone that's done a couple of CA/SR conversions, or a qualified auto mechanic. Having a wiring diagram (from the car that's donated the engine) will help a lot.

ps. CAs and SRs will work ok without an 02 sensor input. No input is an Error condition, and the ECU has facility to "workaround" that error condition. Don't expect it to work great, but you can come back to the 02 sensor issue, after you've got the engine running. Just don't tape up all of the wires.

we've got the engine running
all lights are working as well
and the gauges, aside from the tacho and temp gauge.

anyway

its idling rough

also the main issue is it accelerates very very very slow (NOTE the 3 very words)
it drives fine on 60kph
but still find it very slow acceleration even on that speed

I'm not that good at electrical stuff.

I found out from www.club-s12.org that theres two version of the ECU -1986 & 1986+
but that forum suck cos no one replies on the threads...

thats why Im here the best forum on the internet.