I purchased the SHD version of the RBX a year ago to fit on my MSI K7ND Delta-L motherboard, and then later ordered a brass replacement top and ran into a problem. Tops for the SHD version of these blocks are actually threaded, while the regular 4-hole style tops are smooth bore.
Notice the holes I've circled in the pic you posted. (beware mad paint skills...bleh)
Those holes are usually threaded on an SHD version of the block. I emailed Danger Den about it, and was told to contact the sales department and they'd send me some inserts/adapters. I did not do so myself, as I ended up upgrading to an A64 rig and bought a new A64 top for my RBX.
Just give DD a call or drop em an email and they should be able to help resolve the problem. I do agree, though, that they should have better documentation on their website concerning the SHD versions.