well... you should be able to get there fairly easyish
intake, exhaust, intercooler, intercooler hardpipes slightly larger than stock.. those are the first cheaper upgrades
then you're lookin at upgrading the turbo, i would suggest a single turbo as they're not as much of a nightmare to plumb in as opposed to a twin turbo setup
also the 1jz is very very similar to the 2jz so you could look at what the 2jz guys are doing as mods to their engines
this is the 1.5j (2jz block with 1jz head) that i work on frequently... take a look around
JZA70 R 1jz Supra