Since most Northern CA counties online go back to about to the range of '80-'85 currently, doing the 40 year search is problematic.  Most do allow you to use Assessors Parcel Numbers for research, but unlike out east where it is more common, this is unreliable and not an assured way to find documentation (in fact, relying on it is a good way to miss many documents, so don't rely on it except as a cross-check of minimal value).

As I always say, lower your client costs by getting a digital camera and taking screen photos of the in-county records, otherwise you'll run into tremendous expenses.  (Santa Clara County docs start at about $20 just for the first page of each and go up from there).

A $40-75 search fee range is typical for this sort of thing depending on the location of property and client turn-around needs.  If there are any splits, the cost increases in proportion thereto.  Costs of doc copies, certifications, and any delivery fees are not included.  We discount for bulk orders or regular clients, but not by much.  With the nature of your client's question, we would be leaning toward the higher end of these costs, as all that extraneous documentation is neither typical or easy. 

Consider offering them the basic report plus copy costs at the county fees and mention that they could get the copies cheaper at $7 each from DocEdge.com which is one of them "DataTree"-ish companies.