the gte swap is probably the most well documented swap into the 2nd gen gs300

if done right the shifter is in the exact same place, you want to use to trans out of an aristo for the most direct swap but many guys are running supra tt auto trans and a few have gone 6 speed

a quick search of clublexus brought up a few threads if your not on there i highly suggest joining and reading there are tons and tons of threads about the swap in the 2nd gen GS section

one of the best documented swaps almost could be considered a diy
Turbo Build Diary: Vol. 2, 2JZ-GTE VVT-i Conversion - Club Lexus Forums

a few other i found right quick
It begins. . . - Club Lexus Forums

JDM GTE guys, how many dropped strait in? - Club Lexus Forums


now if your motors strong why not just go single on the ge? depending on your power goals it can be cheaper and just as reliable, there are a few single kits that can get you running for under 2 grand then another grand will get you making some solid power real quick