on the EK's the engine loom is a one piece loom that goes through the firewall and plugs directly into the ECU under the dash on the passenger side.

So you will ask yourself which loom do i Use? The DC2 engine loom has connectors terminating just after the firewall... If this were to swap in a EG it would be plug and play unfortunately its not as easy for an EK!

97 ecu connections should be OBD2A (looks like it on the pics), I would totally utilise the CXi engine loom fit that on to the B18C, add the missing wires and add/extend any wires/sensors that are missing such as VTEC, KNOCK, IAB control and also you will need to wire up the heated O2 (4-wire) as the CXi from memory is single wire.

As for the immobilizer there is a bypass method but if your 97 ecu doesnt have a onboard immobilizer then you might get away with it... However on the EK's they have a separate immobilizer relay unit that I have seen on some models...