Catherine:
I suggest you contact Spacesaver - they have very nice racking/shelving - everything is custom made to suit your needs. Ben Adamitus (708-408-5880, BAdamitus@spacesaver.com) is their museum person.
Sue Maltby, Conservator, Fellow IIC
Maltby & Associates Inc.
Adjunct Faculty, Museum Studies Programme/Faculty of Information, University of Toronto 174 Spadina Ave., #508
Toronto, Ontario
M5T 2C2