Foundation Modeling - Interference Zones

I am somewhat new to Dynamo. Have gone thru the basics and am using packages in Revit. But I have a somewhat easy but likely complex in Dynamo need:

Create interference zones below foundations. One thing to note is I am using Parts in Revit which make extracting dimensions more difficult. I’d love input from some experts on how to start. Or maybe it is much easier than it seems.

See image: http://2.bp.blogspot.com/-aR0XBeyxcNs/UT4kWQgWp6I/AAAAAAAAAHk/5pCPzAMl5k4/s1600/geopier+no+zone+1+-+placement.png