easy peasy
I don't know what fits in tray unmodified, but that's why I said it had to be changed. 1500 ish is probably true, or the 1350 like I put in the 1st location (primary position) and while bigger than stock, it fit perfectly with no mods. By the way, 1350 has better charactristics than 1500 even though the numbers suggest bigger numbers = "better". The 1350 lasts longer even though the CCA are slightly higher in 1500/850cca. Interestingly the 1220/680cca is spec for lr3, 1350/770cca for lr4.
All 4 listed for your comparison
I listed the 1500 before 1350 because I think it's superior. My guess is that the 1500 is "recommended" because it's the easier fit.
1220
http://shop.odysseybattery.com/p/pc1220-a?pp=12
1500
http://shop.odysseybattery.com/p/34-pc1500t-a?pp=12&sort_selection=price_high_low
1350
http://shop.odysseybattery.com/p/pc1350-a?pp=12
2150/1150 cca, 100 ah, 205 reserve which is basically 50% more on all points than 1500 and the 1500 is barely up to spec for LR3.
http://shop.odysseybattery.com/p/31-pc2150t-h
I'd had the Optima yellow and red dual in my 1996 disco and then also in the 2004 disco mainly because back then, in 2001 -2006, I didn't know any better but they also fit well in the tight engine bays. (in a disco 2 you can put 2 optima in side by side turned 90 degrees from factory orientation with a little fiddling. So, it's a slick set up. They never lasted like these Odyssey's though. Could be as simple as quality control.
In the LR3, I think it's really worth reworking the factory trays because there really is a lot of space if you thoughtfully use it all. I have the 2150 on the port side with the item (pump or something) in front of it on a bracket moved forward just enough to still allow then in front of it, before the washer filler, an ARB compressor with gauge and outlet plus piping to reserve tank mounted under starboard side frame/sill cavity using a factory tank identical to what is mounted on port side for air suspension.
for left hand drivers, port is driver side
