The two point conversion did not exist in the NFL until 1994. The only play available for the PAT was a kick. This you had to long snap it anyway.
Actually, you were allowed to run or pass the ball in for a 1-point score for the PAT back in those days. I saw it happen, especially when the kicker was injured or the kick was blocked. So the QB could have lined up under center and kneeled. Nothing forced you to kick the ball.