K let me give u the full history. Both my truck and my neighbors who I bought the swap from are 97. His truck was originally a 4.3 auto truck like mine. He did the swap but had ECU problems which made him set the truck aside years ago. I don't know what year harness it is but it does have the 5 plugs on the ECM so I assume it would have to be 96 or early 97 because I believe late 97 and 98 have only 4 plugs. I did notice 2 differences in the harnesses. There is a square 4 pin connector underneath the brake booster that has no plug to go to it from the V8 engine harness. The wires from the empty plug go down the driver side frame rail so I assume they have something to do with the fuel gauge. Also behind the glove box there were 2 connectors and a black box that was wrapped in foam. The new V8 harness does not have this black box. The main problem with my speedo being off is my tires I was planning on fixing that later on with 411 swap. I plan on getting a cluster from a V8 truck soon to solve the tach issue so my main problem is the fuel gauge.