Gen I PCM = non OBD II inside the car and the size of a football field.
Gen I Crank Sensors. A and B the same. fits 93 to 99. two wire sensors.
Gen II PCM 96 to 99 OBD II
Gen II Crank Sensors 2000 to 2005. They are three wire sensors and they have had many updates. locacted in the front near the oil filter.
Gen III PCM 2000 to 2003 several part numbers all supercede to one.
Gen IV PCM 2004 and 2005. small with three wire connectors
Gen III Crank sensor. 2006 to 2008. just 1 sensor located near the starter. Three wire.
Gen V PCM 2006 to 2008 even smaller, but the most powerfull PCM GM uses.