Which tune up specs to use??
 

My '83 F350 has what I thought was the original 460 engine. However I discovered a sticker on the driver side valve cover while cleaning the grime off. It says it conforms to 1977 emission standards while leads me to believe it's a 1977 engine that was swapped into the truck. Which tuneup specs should I use? The engine decal or the radiator support decal??