The difference in the price isn't the engine per say(variable in availability), its your transmission options. If you go 2jz, then expect to spend 500-700 for the bellhousing/flywheel to put a r154 or w58 behind it. 6 speed is great, but people usually want their second born child for one.
To save you time if you ever need help with fabrication, I would honestly hit up Alex. Guy knows his stuff.