is the under dash wireing harness the same on a 1997 ford f150 the same fore the v6 and v8 modles

 

Under the dash, it should be, but under the hood , the engine harness and ECM wiring will be different.

 

The engine harness for the ECM might be the same - but the ECM itself different, and/or with a totally different program stored in it.

For each year you can expect many basic parts to sustain several different engine and driveline packages. But the essential items, the engine, ECM, the sensors - those will be interchangeable.

But again I say MIGHT be. I think it PROBABLY is - but there's only one way to find out, we need an answer from Ford or we should look up the wiring diagram. My guts tell me they would have made it "Plug&Play"