Brendan,
We may just have to disagree on this, but I will try to explain why John 6 is not talking about the Eucharist. In John 4, Jesus meets the Samaritan woman at the well. She is getting water for drinking. Jesus, uses this opportunity to teach the woman by using her immediate need, water, as a metaphor to salvation. He says to her, “Give me a drink” (John 4:7). She questions him
“If you knew the gift of God, and who it is who says to you, ‘Give Me a drink,’ you would have asked Him, and He would have given you living water.” (John 4:10)
“Everyone who drinks of this water will thirst again;
but whoever drinks of the water that I will give him shall never thirst; but the water that I will give him will become in him a well of water springing up to eternal life. (John 4:13-14)”
Jesus has turned the conversation from getting water to salvation, “living water”, that he gives. Water here is a metaphor, there is no literal water somewhere that gives eternal life. He is talking about believing in Him as the living water. And that belief in Him is salvation.
After this, Jesus’s disciples came to him and urged him to eat. Obviously he has not eaten in a while.
But He said to them, “I have food to eat that you do not know about.”
So the disciples were saying to one another, “No one brought Him anything to eat, did he?”
Jesus said to them, "My food is to do the will of Him who sent Me and to accomplish His work.
"Do you not say, ‘There are yet four months, and then comes the harvest’? Behold, I say to you, lift up your eyes and look on the fields, that they are white for harvest.
(John 4:32-35)
Again Jesus is using the immediate need, in this case food, to teach the salvation message. A metaphor this time with food. The harvest and the white fields is another metaphor indicating the approach of the Sumaritans after the woman at the well told them of Jesus.
John 5 again Jesus is teach that eternal life is believing in him.
"You do not have His word abiding in you, for you do not believe Him whom He sent.
"You search the Scriptures because you think that in them you have eternal life; it is these that testify about Me;
and you are unwilling to come to Me so that you may have life.(John 5:38-40)
Remebering John stated that Jesus is the Word became flesh, Jesus again is teaching that belief in Him is eternal life. He states that the Jews search Scripture for eternal life, but they do not find it, because they reject the living Word, Jesus.
John 6, Jesus feeds the Jews with the miracle of the 5 loaves and 2 fish. After all have eaten, Jesus left. The Jews then searched and found Him. Jesus then states
"Truly, truly, I say to you, you seek Me, not because you saw signs, but because you ate of the loaves and were filled.
Joh 6:27 “Do not work for the food which perishes, but for the food which endures to eternal life, which the Son of Man will give to you, for on Him the Father, God, has set His seal.”(John 6:26-27)
Jesus knows these people where searching for him for more food to each. And just as Jesus told the Sumaritan women,
“Everyone who drinks of this water will thirst again;
but whoever drinks of the water that I will give him shall never thirst; but the water that I will give him will become in him a well of water springing up to eternal life.”(John 4:13-14)
Jesus tell the Jews to not work for food that perishes, but for the food that endures to eternal life. Jesus again is using the immediate need as a metaphor for the salvation message which is believing in Him.
What is telling with these two stories is the response from the audience is the same. After Jesus tells the woman about the living water, she states “Sir, give me this water”. The Jews about the living bread give the exact same response, “Lord, always give us this bread.” Jesus knows how to reach the people with the message of salvation by tieing it to their immediate need. I think this is great. The living bread and living water is belief is Jesus.
When Jesus says that he is the bread of life and to eat his body and drink his blood, for eternal life, this again is the same metaphor of food representing salvation. The entire topic of his teaching began because the Jews were hungry and wanted more bread from him. He ties this to receiving Jesus, believing in Him, for the food that never parishes.
After Jesus made this statement, the Jews again took it literally and was repulsed by it.
Then the Jews began to argue with one another, saying, “How can this man give us His flesh to eat?”(John 6:52)
Even some of his disciples took this literally and walked away from Him
Therefore many of His disciples, when they heard this said, “This is a difficult statement; who can listen to it?”(John 6:60)