451 overheating, even when moving

That fan is too close to the rad. Engine movement, body flex etc & the fan may contact the rad....& take it out.
I would get a shorter spacer....or take the current spacer to a machine shop & have 1" removed from it.
I agree. If you have a way to cut it straight, I would cut that spacer in half. You could try it without the spacer, but the fan may hit the pulleys then. I'd sure try it. IT's way too close. Sounds like you're gaining on it though.