100+ year old multi-family: Broad ACV or Basic RC?

[Dana Yobst]

I've got a curve ball in insurance on a property that was built 100+ years ago.  I have a number of other properties like it and mostly bought special coverage replacement cost (RC) and one property has broad ACV (actual cash value).  Now my options are limited (for reasons i won't bore you with here) to basic RC or Broad ACV.  Recommendations?  Also, is it difficult/painful to switch insurance once you insure for close?