The Quad 14' MkIII (N) are the guns you're looking for on the PoW. Those are level 76 guns
so you should be able to mount them on your front turrets with at least 5 binds of ammo
each. The second R turret is small so the front and rear turrets can hold more ammo/larger
guns, but this is the most popular setup.

Alternatively you can mount the Quad 14" L on your front and rear turrets and the Dual 14"
L on your second R turret. However, only the Quad-N guns blockshoot so your spread will be
a bit wide with the Ls.

Oh...i can only equip one Quad L, up front....well thats weird.

Im pretty sure L is not in my list. only MKIII and D

L stands for Longer range and a little slower reload.
D stands for Shorter range and faster reload.

They are different versions of the same gun. Shell damage is the same.

I think you should be able to see the mark III L with Pow, as it is lvl 76,
just be sure to select one of the two big R mounts, as if u check
Pow has 2 R slot sizes: 457(which is enough for 14"quadsmk III L)
and 388 (which is enough for 14" DUALS mark II L)

Don't Know Uk guns but L is long range [less damage] D is damage [less range] N is normal
[in-between]