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Where should I run a standalone LS harness into the cab of a 72 without drilling new firewall holes?
- E38 ECM is sealed and underhood-safe but must avoid heat and splash. (applies to E38 ECM; Chevrolet Performance NA LS control kit 19171935; LS2/LS3/LS376/LS7/LSX454; 58x/4x; 2006+)
- E38 connectors use slider-bar latches. (applies to E67 ECM; Chevrolet Performance LSA E-Rod control system 19299067; LSA)
- PCM mounts inside the cabin through a 2-inch firewall hole. (applies to 0411 PCM (GM service #9354896 or 12200411); 1999-2007 Vortec DBC (LM4/LM7/LQ4/LQ9/L33/L59); T56 or non-electronic automatic)
- Starter uses large black ring terminals; heat-sleeve wire under the manifold. (applies to Gen III PCM; Aeroflow AF49-1505; LS1/LS6; DBC; 4L60E/4L80E)
- Harness splits at the firewall grommet into engine and underdash sections. (applies to Gen III PCM; Aeroflow AF49-1505; LS1/LS6; DBC; 4L60E/4L80E)
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Confirm against the instructions for your exact parts before wiring. More: Harness and power in our tuning guide.
Use the stock wiring harness hole in the firewall or the unused clutch linkage hole; both get the harness into the cab without drilling. In the builds we've seen, tucking the whole ECM inside the cab, for example in a mount near the glove box, is the usual choice rather than passing only the gauge and ALDL wires through. A PSI standalone harness comes with its own grommet for the pass-through.
Check this first:
- Check whether your harness includes a grommet (the PSI harness does)
- Make sure the hole edges are protected so the loom can't chafe
Based on what we've seen work across our own builds, our friends' builds and the wider LS community, reviewed by our lead shop tuner (over 20 years of LS and LT tuning experience). Every combination is different, so use at your own risk and check our safe tuning limits before any wide-open pass.
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Every option we know of
| Maker / product | Part # | Fits | Price | Where | Status / notes |
|---|---|---|---|---|---|
| Dorman 8-pin Metri-Pack 150 connector (unverified lead) | 926-309 (not independently verified) | Some LS engine harnesses | varies | Buy parts stores | Unverified Confirm pin count/series before ordering |
| Aptiv / Delphi Metri-Pack 150 connector shells and terminals | varies | OEM-style repairs | about $1-5 per shell | Mouser, Waytek | Current production Match series and pin count |
| Generic 16 AWG automotive wire | n/a | Main engine-harness runs | about $10-20 per spool | parts stores | Current production Match factory gauge; don't go smaller |
Prices are approximate as of September 2026. We list every option we know of, including small shops and used parts we can't link to. Confirm fitment with the seller.