L67 - Series II Supercharged 3800
L26 - Series III Supercharged 3800
Gen 3 - Refers to M90 generation used on Series II motors. Slight design changes from older gens such as the ones on the 3.8 Tbird Supercoupes.
Gen 5 - Refers to M90 on Series III motors. The supercharger has a larger opening in the base, smaller silencer slits, and a different rotor coating. It's more efficient than the Gen 3 at making boost without heat, which is why so many people try to get one. They also don't generally need porting whereas Gen 3s do.
LG8 - 3100 motor.