I wouldn't recommend Interstate batteries/Johnson Control. They last just long enough to get through their weak warranty. Look at who offers the longest free replacement warranty. Land rovers are hard on batteries.
Agreed, not a huge Interstate fan.
I made some mods to my rig to accommodate a group 31 battery. I can walk somebody through it if you really want to, but you can get nearly as much power from the OEM size (group 94 or something...have to look that up).
I went with an Odyssey AGM sold through Sears as their marine Diehard Platinum. It's a hell of a battery - if you have the ability to charge/maintain it. And few people do -it's very particular about the specs and a stock Rover's alternator/regulator won't do it. So about 6 months in I'm ready to replace it.
I'll be sticking with AGM for a couple of reasons. First the low self-discharge rate. My truck sits for a week or 2 pretty regularly between drives since it's not my daily driver. Second is that it's fully sealed; you could literally mount it upside down if you wanted and it won't leak or outgas (unless you seriously over-charge it). And lastly, AGMs make a good deep cycle platform which is what you need for house loads like a winch, fridge, lights, etc.
Probably the best deal on an AGM would be the Dekka Intimidator line. I'm considering this as a replacement. The group 31 is under $250.
The battery I want to use is the Northstar AGM group 31, but I need to do some checking. The specs say it's 4/10" taller than the other group 31s, which won't fit for me. I'm super-tight on vertical clearance to the hood and I wouldn't want to give up that space. It's also more expensive than the Dekka, clocking in closer to $300. But it's the closest match spec-wise to the Odyssey.
Tomorrow maybe i'll pull the Odyssey out of the LR3 and take my own measurements to see if the Northstar will fit.
In the past, people had good luck with Optima, but then they moved their manufacturing to Mexico and the quality went to hell. I've heard rumors that the latest production is beginging to get back up to snuff, but I haven't event bothered to look up the specs on their group 31 to see how it compares based on the many negative comments I've heard up till now.
Again, remember you can't fit a Group 31 in an LR3 without mods. It can be done but it's not a drop-in.