I've seen these in the Demon Tweeks catalogue/website and they look pretty much the same as the DP ones, but less than half the price!
My only question is whether they have the mouting points for the original heel plates, or if you need to replace them with different ones (as per the DP items).
As Andy says, the Corse ones mount on the same mounting holes as the rearsets themselves - that's why the Corse heel guards are a weird shape!
The sparco ones in Demon Tweeks look like they have mounting points for the original guards, so I might just give them a go. They don't have pics of the 916 ones in the catalogue or on the website though, and I can't find any pics on the intarweb either!