Basically ShivanSPS takes the SCP releases and uses them to build a pack which makes installation much easier for people new to the SCP. Shivan's pack includes the original game (although there are other ways to get hold of it too). The idea of his release is that you simply unpack them and you're done.
ShivanSPS bases his packs on the latest builds so if you're trying to build your own what you'll have to do is.
1) Get hold of
and install FS2
2) Install a recent build
of FS2_Open along with the launcher and recent mediaVPs
3) Install the mods ShivanSPS included (FS1 Conversion
if I remember correctly)
There's a guide on how to install SCP yourself in my FAQ. Till ShivanSPS started making his packs installing it manually was the way most people got it working so it's not that hard. It's up to you whether you want to wait for him to be done with 1.8 or to do it yourself. There's nothing in his pack that you can't get elsewhere. All he does is make it a lot easier to find the bits and install them.