I'm not really flashlight guy. Guns yes flashlights not as much. I have ad Sure Fire 6Z combat flashlight bought back in 2008 this along with the Maglight are the two I want to make better! The 6Z still hangs out in my squad is it a P60? Like I said I know about nothing just light bright or not bright is about it when it comes to flashlights.
Brother, as one gun guy to another - be careful, cool flashlights are addictive. An Oveready custom 6P in natural HA looks just like its been parkerized - matches my Mk18 perfectly.
I had liked'em so much I had to have a couple - one for the Mk18 and another for a recce.
To answer your question, the 6Z is a "P60 host." I'd drop in a Malkoff M61 and not look back (I've done that for all my old incandescent SF classics - mostly 6P, and C2).
Malkoff products have a great record in police and military use and an M61 will not only give you much more light output, but longer run time and greater durability to boot.
If you use your 6Z with the Rogers technique (involves holding the flashlight in your off-gun hand between the middle and ring fingers and activating the tail switch with your palm), the original Z41 tailcap is perfectly adequate - its the way I carried/used my C2 for years. If you want a clickie switch, I'd consider an original Z59 tailcap or a McClickie (Malkoff switches use McClickie as well and will work fine with SF classic series lights).
Stay safe
