I bought the belt that the OP has on his 2UZ, I'll try it to see if it works, but like you say I know quite a few people have used this belt with its lesser fan pulley contact arc, so it must work. It not then it would be easy enough to fab up an idler pulley.
I guess I could ask the rhetorical question, why would you want to put your battery inside? I'd rather have a more cluttered engine bay than have a battery stuffed somewhere inside the passenger cabin. On the earlier 40 series (mine's an early '72) you have to remember the gas tank is already inside the cab under the passenger seat and there's a tool box under the driver's. I don't really want the battery behind the seat or anywhere else in the rear passenger area. Batteries are hydrogen off gassing, nasty, heavy acid filled boxes, if it were to fail somehow, no matter how remote, I'd prefer it do that in the engine bay.
I think there should be enough room on the passenger's side of the engine bay somewhere, the only thing is that the 2UZ is a big motor compared to a Chevy V8 so it will be tight. I was just wondering where the OP was going to place his that's all, but of course he has tube fenders so he will have more room to place it in the engine bay if he chooses.