Can I simplify the stock GM harness myself instead of buying a custom one for a buggy swap?

Here is what the documentation says. Each point links to its source; details depend on your exact computer, harness and transmission.

• 0411 PCM (GM service #9354896 or 12200411); 1999-2007 Vortec DBC (LM4/LM7/LQ4/LQ9/L33/L59); T56 or non-electronic automatic: PSI HAR-1019 fits 1999-2007 Vortec DBC with T56 or non-electronic auto. (PSI Conversion)
• 0411 PCM (GM service #9354896 or 12200411); 1999-2007 Vortec DBC (LM4/LM7/LQ4/LQ9/L33/L59); T56 or non-electronic automatic: Harness uses GM Delphi connectors and cross-linked 600 V wire. (PSI Conversion)
• 0411 PCM (GM service #9354896 or 12200411); 1999-2007 Vortec DBC (LM4/LM7/LQ4/LQ9/L33/L59); T56 or non-electronic automatic: HAR-1019 deletes EGR, AIR, CCP and rear O2 wiring. (PSI Conversion)
• E38 ECM; Aeroflow AF49-1506; 58x LS3/LSX; DBW; T56 or non-electronic automatic; 2006+: AF49-1506 deletes rear O2s and emissions-device wiring. (Aeroflow Performance)
• Gen III PCM; Aeroflow AF49-1505; LS1/LS6; DBC; 4L60E/4L80E: AF49-1505 deletes rear O2s; front LS1 O2 is GM 25161131. (Aeroflow Performance)
• Gen III PCM; Aeroflow AF49-1505; LS1/LS6; DBC; 4L60E/4L80E: AF49-1505 engine section retains injectors, coils, sensors and transmission wiring. (Aeroflow Performance)
• Gen III DBW: blue/green P59 PCM; Gen III DBC: red/blue 0411 PCM; 1999-2007 Vortec; 4L60E/4L80E: BP Automotive deletes EGR, AIR, EVAP and rear O2s in standard form. (BP Automotive)
• Gen III DBW: blue/green P59 PCM; Gen III DBC: red/blue 0411 PCM; 1999-2007 Vortec; 4L60E/4L80E: BP Automotive: DBW uses blue/green P59, DBC uses red/blue 0411. (BP Automotive)
• 0411/P59 factory harness strip-down: DIY harness stripping: depin unused circuits and plug empty cavities. (LSX Magazine)

Confirm against the instructions for your exact parts before wiring. More: Harness and power in our tuning guide.