The sensor is optical, not magnetic, and I have seen this done on a thread somewhere. You will need to bring the reluctor wheel with it also. The engine will run with the low res signal only, or since your bringing the whole deal, might as well have it use the high resolution signal as well. I have read the sensor is made by Mitsubishi, but I don't know of a source for one, except an opti. You may have a rough time getting the sensor and wheel to fit inside a normal HEI as well. I'll see if I can find that old thread, may have been on camaroz28.com or ls1tech.
Crank sensor is useless, it detects misfires only, it does not control spark.
High res is for fine tuning injector and spark timing. The spark is controled by the pcm using the input it gets from the opti. The pcm tells the ignition module when to fire the coil.