Those 2jz that are pushing that much horsepower also have a ton of money put into them. The turbo alone on one of them is probably Anywhere from 2-5K. Our cars are also fwd which doesn't give us a lot of options for transmissions. The supra being rwd all you need is an adapter plate and a custom flex plate and you can bolt on a wide range of transmissions. A guy doing a 2jz swap into a 240's that I know used a built th400/turbo 350 transmission. So like matt said the transmission is what limits you.