The M3T + A19 = Four-SF123A body requiring the MN60 or MN61 lamps.
The Millennium TurboHead is used by the M3T, M4 and M6.
However, each flashlight has its own lamp assemblies.
The M6 is not six-SF123As in series. It is actually two parallel sets of three-SF123As in series.
This means it is more like a 9V light than an 18V light.
However, it is far too powerful to run the M3 or M3T lamps.
The KL6 is an LED bezel with a LuxeonV in a reflector.
This can be used on an M3/M3T body.
This "combination" is the basis for the L6.
The KL6 can also be used on the M6 body for longer runtime.
I'm not 100% certain but I don't think the KL6 can be used on the M4 body. I wouldn't risk it without confirming with SureFire tech support first.
The M3T can also use the N2 lamp assembly. Although the M3T was not designed to use the N2 lamp it can be used in a non-critical capacity (due to the N2's shorter outer spring contact it may not provide 100% contact in abusive situations such as after a drop or after been used as an impact tool) The N2 lamp should not be used in WeaponLights for critical applications.
I presonally use the N2 in the M3T instead of the MN15 because it has a more round beam which I find more attractive.
You have a number of TailCap options for the M3.
SureFire offer three main Clickie TailCaps - the Z48, Z58 and SW02.
There is a discountinued SW01 non-clickie TailCap which is a pressure switch LockOut TailCap but styled like the SW02 (without a rubber shroud). I don't have one though.
Al