wait so you have a v8 ecu?
you would need to pull of the dash to put in the rest of the wiring, because you need wires to go from the engine harness to the ecu and it will connect to the speedo and stuff, which you may have an issue with, plus running all the wiring.
i dont know, im no expert in the swap department, if i saw a wiring diagram i could help more, but i dont even think your RS ecu harness will connect to the V8 ecu will it? that is the problem, your V8 ecu needs wires for the avcs, TGV's, TBW, etc...which your current RS harness doesnt have. you may have empty slots to put them, but its still prob not gonna plug into the V8 ecu, unless you have already checked.
like i said i cant really tell from your wiring diagram but from you typed about the crankshaft sensor, you have the right idea, you need to match those up.
Ben