Yes, the KL5 bezel is the same bezel as used by the L5.
No, the KL5 will not screw onto an L4 (E-Series) body.
I've not attempted to attach a KL5 to the adapter collar from the LU60A Lamp Module. This adapter collar allows an "M2" bezel (and Z44 "6P" bezel, and I assume Z32 bezel) to attach to the E-Series body.
Note that SureFire have discontinued to the KL5 bezel. It's 'Replacement' is the KL5A bezel which is similar but features a new LED.