Those look to be modified. The 2 sets I have (both being used right now, so I can't check them) have the end plates being straight up. Yours seem to be modified with one hole slotted, allowing the end plate to be tilted, which would effectively move the shaft back, and a bit lower, which would require the stands to be milled a bit. Not sure why anybody would do that, but being used by a racer, it's anybodies guess as to what they were modified to fit or work with.
Edit: Now I'm not sure. The stands look a bit short to me, and I can't remember 100% if mine were tilted like that or not. The "slot" I mentioned may just be a shadow, I can't see for sure. Either way, like Tom said, Oregon Cams doesn't make a set for a HR because of the reasons he stated. Not enough room between the shaft and plate for the rocker.