I don't want to be too discouraging, but I doubt you'll find one.  It would mean comparing every object in the drawing separately to every other object, looking at relative position and size and linetype and possibly Layer and so on and on, and compounding that with comparing each to multiple-object groups of potentially-related objects, and keeping track of what relationships have been identified.  When you add in the possibility that some of the machines, etc., were likely rotated at different angles, it becomes hugely more complicated.I think if a Block had been made of a very few simple pieces with an easily defined relationship [e.g. a Circle with a Line across it whose length matches the Circle's diameter and whose midpoint is at the Circle's center], there might be some hope of finding such pairings, but the complexity of the problem expands exponentially as the number of objects increases, and it sounds from your description like such a routine would have untold millions if not billions or trillions of comparisons to make and keep track of.