Basically I wanna start small with this build and I’m new to the car community, but I have a lot of experience in mechanics. I want to ditch the 4 speed gearbox and swap ECUs to a standalone I just don’t know what or where to look for compatible parts

 

You probably will find most of your answers online. There may be some threads here if you use the search, but you'll see more owners exploring this on Lextreme forums and some videos on YouTube. I would start there

 

i would use lextreme for any "hot rodding" of the LS400 platform especially manual swaps and standalone ECUs. also lots of aussies down under have had great success with standalones on their 1UZ swapped cars - i just don't know what forums they use.

there are a few folks back in the day here that did some attempts to manual swaps but i've yet to see one completed.
case in point: https://www.clublexus.com/forums/bui...car-build.html