If all you have is 2D (DXF, DWF, PDF, etc.), then you can use them as references to create 3D objects that can then be converted into a Block. The Blocks can then be placed as needed.
First, make sure that the 2D references are accurate (you may have to scale in X or Y, or even redraw according to the dimensions).
Then, you can Simple Extrude the 2D references, even going so far as rotate and position various views (XY, XZ, YZ) so that they can overlap and 3D Intersect to produce the desired object.
TC Pro Platinum 2017, 2016 & 2015 (all with LightWorks) & V21
System: i7-5820K @ 3.30GHz, ASRock X99 Extreme4, 16GB DDR4-2133 RAM, Gigabyte GTX 970, Samsung NVMe SSD 950 (256GB), Windows 7 Pro (64-bit) SP1