The last GT45 ebay turbo I've seen on a 2JZ was hitting boost at 5k, with power coming after. Complete waste of time for a street car in my opinion.
If your budget it tight you can try a ebay T4 T70 or GT35 turbo. Both sizes will kick in around 4k. You can also find Borg Warner S300SX3 63mm turbo's on eBay for £575, which is pretty cheap for the performance you will get for your money. Those turbo's will spool in the late 3k to early 4k rpm range.
I've been advised recently that if you are running the NA autobox you will be limited to around 300 ft.lbs of torque before you kill it, regardless of how many coolers you put on it.
The TT boxes take more abuse, and I believe DavidP can build you a hybrid autobox good for even more power if you bring him the right bits.
You can achieve 450hp on an unopened 2JZGE but you will be starting to reach the limits of knock on regular pump fuel at that sort of level. Advisable to put a TT headgasket and/or TT pistons into the engine to drop compression. Or start running meth injection/knock resistant fuels.
The distributor ignition system is a point of failure for sure, but there are a few guys running 400-500 NA-T's with distributor. See if you can get away with it on yours before upgrading.