Alteringing elements elevations


We have several models of buildings dating back a 100 years or so,.
In regards of new adjustments of theese buildings we feel that new elements, such as beams/coloums etc.
should be modeled in a new revit model. When the project is completed, the new model is imported into to the existing model.

Importing, as I see it, works best when the materials, levels etc. is aligned. However, the existing models is not modeled by people experienced with construction.

So my question is: Is there a way with to extract base constraint and offset of elements, adding them and setting it as new offsett to to new level called level 0, at elevation 0?