Would a V6 get better fuel economy than a V8 in a heavy late 60's car?

Would a V6 get better fuel economy than a V8 in a heavy late 60's car?
No it would be approximately the same because a V6 is a smaller motor and would have to work hard to move the heavy car. the V8 is a bigger motor however it doesn't take as much power as the V6 to move the same amount of weight.