T105 is almost universal, that size limitation has been what has prevented me from moving to higher voltage 12v T1275's in my one car for more speed.I have to agree with JRP3, I don't think you need to copy lead acid sizes.
One exception to that may be the Golf Cart battery sizes (GC-1, like the T-105) because there is such a large installed base of a single size. Those are used in more than golf carts and old EVs.
He does not need to copy that size BUT the size should be divisible by it so you can fit lithium batteries into the footprint evenly, it is a real pita when you want to upgrade to both lithium and more voltage and the darn things do not fit well leaving a huge gap in the compartments.
That is one reason I don't have NiMH in my car right now, long and skinny packs so I couldn't fit them easily into the battery boxes and also couldn't fit enough voltage in as is without cutting and welding Al.