seeking help identifying ECU wires

[Datsun]

I am in the process of putting a SR20DET into an 1969 MGB. This is a long term project that will probably take me years. I have the engine sitting on a stand in my garage with an intercooler and a radiator hooked up so I can run it. My question is about some of the wires coming out of the ECU. Some of them I will obviously not need like the ones that operate the air conditioning (no AC in the car) or the ones for the automatic transmission (I am running the standard transmission) but I am confused about some of the others that the engine seems to run fine without. Of course the info I have here I found on the net so it may or not be correct.

#34 Start signal from ingintion switch (orange) I guess this sends juice to the ECU when the key is the start possition. Anybody know why?#105 Fuel pressure module (red/white) I thought the fuel pressure was controlled by vaccum. Can anybody tell me where this wire runs to and what it does?# 26 Exhaust temp sensor (blue/yellow) Aparently this runs to a temp sensor behind the cat. I won't be running a cat on this vehicle and would rather not bother with this. Is this sensor important for proper engine operation or is it just for the high exhaust temp light on the dash? #14 CLK clock-timing signal (green/white) I don't know what this wire is for.#23 CHK check start (green/red) Here is another wire that right now is connected to nothing.#45 Ambient air temp sensor (blue/white) I am assuming this has something to do with the air conditioning and I don't need it but it anyone thinks different please let me know.

So right now this engine fires, runs and sounds good but I don't want to leave these wires off without know exactly what they are for. Any help here will be greatly appreciated.