Keith -
Do you already have the Valley Cement kit? If so, look at the box - there's a "footprint" diagram on the side. (I would have scanned it and posted it here, except it's a copyrighted image so I figured I'm not allowed to do that.)
You'll notice the way they have it laid out, it's just under 24" wide - meaning it would just barely fit in your 2'-wide space. I'm facing the same problem, so what I'm planning do to is: Rather than have the siloes out toward the front like they do, I'll extend the silo conveyor in a linear (rather than perpendicular) direction from the kiln building, with the siloes against the backdrop. This cuts the width requirement almost in half, leaving space for the main line right-of-way and interchange track. (Of course, this will require some kitbashing mods to the areas connecting with the conveyor.)
Good luck, let us know how you work this out!