I have a 1995 Chevrolet c1500 4.3L. I’m in the process of swapping the engine out for a 1993 350 and I’m just trying to figure out what to do. I’m assuming I’ll need a new engine wiring harness for the year of engine and a new ecu. Is that all I’ll have to change up? Is there any place you can suggest to find a 350 harness cause I have looked everywhere and I cannot find one

  • Welcome to Motor Vehicle Maintenance & Repair! Commented Jan 24, 2023 at 10:17

1 Answer 1


I've not done the the swap you're talking about, but I have a good idea of what you're going to need. I'm going to break this down into two separate areas, mainly "needed" and "possibly needed".


  • Engine
  • ECU for new engine - This could be eliminated if running a carburetor and HEI distributor. An HEI just requires power and provides the timing portion of the ECU ... all in one package.
  • Wiring harness for new engine - If going carb'd/HEI, much of the old wiring harness could be adapted to get it running
  • Exhaust connection - Plan on it not mounting to the exact same position as the V6. Welding may be in order to fix this, or possibly getting a V8 Y-pipe to attach to the cat (if using).
  • Air intake system (air filter) - The two will most likely not be compatible.
  • V8 radiator - The V6 radiator is not going to be enough.

Possibly Needed:

  • Transmission & torque converter - Assuming the current is a 4L60e and will bolt up to the new engine. My understanding is the ones used for a V6 weren't built as well as the ones for V8s (if you can consider the V8 ones built well enough for their intended purpose). The V6 torque converter may not be at the correct stall for the new engine.
  • Upgraded fuel pump - Not sure if the V6 and V8 have the same fuel pressure requirements.
  • Motor mounts - Most often, the V6 and V8 do not share motor mounts
  • Reconfiguration of the K-member - The K-member supports the engine as well is what the front suspension ties to if an independent suspension up front. Quite often, the K-member is different between the two engines, though bolt in of a V8 K-member is usually fairly painless, unless you live in the rust belt (for obvious reasons, lol)
  • Oil Pan - If the K-member doesn't need to be changed, there is a large chance the oil pan on the V8 may interfere with it and would need a different type (or modification) in order to work.

As far as a wiring harness, if you're still going that route, I can't recommend one for you as we don't do that on this site, but if you look to a company called Painless (no affiliation), they may have what you need.

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