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The VQ37 HR is not just a DE with more displacement. If you're talking about an '07/08 HR engine, I still don't think it will work because the VHR is a different engine. you would have to ask an engine shop who knows about the water passages to find out if they are the same. but aren't you going to have smaller valves with those heads? I think you can get a whole engine for $2,000. so just look around for some VQ37 heads.
If you have an HR, you can swap in the 370 short block and keep the HR heads. Pretty common swap the HR guys have been doing to get a little more displacement.