Rechargeable battery for stock SF M6?

I have an old, stock, incandescent SureFire M6. I want to keep it stock and incandescent, but see that SureFire now carries only lamps for the E2 and 6P type models. Lumens Factory carries a 450 lumen lamp that I could use, but it got me to looking at the LF HO-M6R lamp...if I used rcr123 batteries in the stock battery carrier for the M6.

I did some searching, and found some very old (2008) threads that say that rcr123 batteries work fine with the HO-M6R lamp in the stock M6. More recent posts seem to indicate that the 16340 battery (replaced the rcr?) is the one to use. So the question is, which 16340 battery is "best" and "safest" to use? I am NOT tech savvy and if available, want a protected, "plug and play" type of battery/flashlight. (FWIW, I have a Nitecore intellicharger, so if I can use the same charger, that would be best.)

If I need to stick primaries and the 450 lumen lamp, so be it. Thanks for any advice and opinions.

fivemega, thank you very much for your reply. Yes, I do know that the HO-M6R will NOT work with primary lithium batteries. I also read that the 16340 battery in the MB20 is NOT optimum...it's just that I have "only" the stock battery carrier. Besides, isn't the 3x16650 battery carrier a "custom" item that is no longer available (commercially or custom), except perhaps from time to time in the Marketplace? I guess I'll give the 16340 batteries a try. Any recommendations as to "best/safest" brand? Thanks again!

Also some 2x18650 adapters can be still obtained, for example CPF user altermann is selling them - but those are only for unprotected cells. You could then buy a bi-pin adapter and bulb from Tad Customs (tadcustoms.com). He sells a MN7225 bulb which is a 2.5A 400+ lumens bulb - not the brightest one, but with 3500 mAh 18650 batteries you will get extended runtime (1.5h+ hours?), these bulbs are 4$. There is also a EO-M3T (9V, 450 Lumens) bulb from Lumens Factory that would work with a 2x18650 setup. Or IMR-M3T (7.4V, 700 Lumens) if you want maximum brightness out of two IMR cells - but this will only last for 25 minutes.

Just for FYI, I use 16650 cells in my 6P and G2 lights, which were designed for 2 CR123 cells. I do have drop ins that work with the 4.2v output, but as long as your electronics will work with 4.2v, it shouldn't be a problem. Also, remember that two 16340 cells in series can output up to 8.4v, so factor that in as well.

Thanks for all of the replies! So many options/configurations. Now I'm more confused than ever. Didn't even know that a 3x16650 battery carrier was still available. Thanks for the info and link...which led to me to other tempting products. (fivemega, pm sent)