Is it LEGAL????
Check your state laws. I legally re bodied my 79' F-150. The frame and body were from two different trucks. I had the titles and bill of sale to both. Had to get inspected by the Sate Police to verify VIN's against theft. I was good , they gave me a new title, VIN and since the body was a 76' they dated the model year 1976. Ethics don't play into this as long as your upfront about what you did/have, have the proper paper trail in do it in accordance with the law.
Ask your local DMV.