http://www.lifelinebatteries.com/rvdeepcyclebatteries.php

Lifeline is perhaps the first step down from what most consider the best
available - the Rolls Surrette batteries - followed by Trojan. Reserve
capacity and cranking amps are mostly immaterial in choosing a true deep
cycle battery. The GPL-27T I am using is 100 a/h and will fit, length and
width wise, in the stock, unmodified box. Deepening or lengthening the box
to retain a stock appearance is important to me. The 'NC-27' battery you
refer to is an inexpensive Exide product and 'dual-purpose', i.e. not a true
HD deep cycle.

Regarding charging: the link provided above seems to relate to
small-amperage chargers designed primarily to charge small batteries.
Xantrex makes several charge regulators for alternators:
http://xantrex.com/power-products/power-accessories/alternator-regulator.aspx
I plan to add one of these to my rig, since I'll be using two identical
GPL-27 batteries for storage (200a/h). Connecting this is a little more
difficult with a Bosch alternator but can be done. Also, there will be an
on-board charger (most likely an Iota) for the times when I have access to
110V power and want to top off the batteries.

Karl