E380: This is a "circulating gear" or rotary shift drum. Lets you shift constantly in one direction...so shift up to 4th gear, next up-shift and your in 1st again. Needless to say...these suck! Only use this if that's what you already have. It may be possible to convert this to a normal shift pattern.
E379 & E402: These are for 3 Speed Plus Reverse transmissions. NOTE: E379 has been replaced by E402 (they are identical except for the guide washer behind the shift star). It's best to use the guide washer but if you need to remove it, you can do so easily.
E381 & E382: These are for 4 speed 1 down 3 up transmissions. The only difference between them is, E381 has a guide washer for the shift mechanism E382 does not. These are interchangeable. NOTE: I'm sold out of E381.. you can use E382 (if you want a guide washer you can take it from your old drum).