Working on my swap and thought there would be enough room for the factory ECU and the LS to reside in the same location. After taking the dash apart I noticed that there isn't, and if I replace the 90 ECU with the swap ECU it should fit.

Now, does the factory ECU even need to be left in the vehicle? Or can I remove the harness and its related components in favor of the new standalone harness?

I'm using a 4l80e with a Nelson harness.