Just make sure if you buy the 1jz by itself hope it comes with fly wheel but make sure it came out of a JZA70 it haves a two row pinned ecu & the right sump configuration.
For first time swaps I would recomend getting a clip ~2000
It will have your IC tranny all your parts etc... ecu sensors easier to do the swap if it is your first time.
If you plan to build a 7-800hp 1JZ before you even swap the engine or drive your supra you have to know what your doing pick a good standalone like stinger, top feed rail upgrade fuel system injetors etc fuel pump fuel lines ic exhaust plumbing & turbo itself then getting the engine b itself is ok but you need to plan this how fast you want to drive this etc...
with 1jz clip and simple upgrade to Y pipe while engine is out use oem parts etc you could have about 300-333 rwhp but twins wont last long above 15psi boost so plan on getting a single in 6 months if you drive it around first on high boost.
You decide...