it says 8/77 on the body, but on the back side of the hood says 1978 model year for emission control stuff.

what year is this car? what year should I reference for parts, service manual and other specifications?

What's the VIN? Aug/Sep was typically the transition date between US model years so it's likely that you do have a very early 78.

thanks.

it's HLS30421935

According to the Victoria British catalog (not sure if it's accurate), 78's started in 8/77 with HLS30-4200001. As others have pointed out, model years are more of an American thing and there wasn't always a precise switchover.