I think one of the first steps to dealing with this issue is standardizing what "Shipping From" information is stored. uc_quote uses two tables, uc_quote_product_locations, uc_quote_manufacturer_locations...i'm going to create uc_quote_seller_locations and work from there.

ATTN: Ryan.

Did uc_manufacturers used to be in core? Seems like uc_quote is in love with it.