Reserving Purchase Order Lines to Work In Process Jobs

Does anyone know how one can reserve purchased items to WIP jobs?  We are an Engineering To Order company and purchase a large amount of items the are specific to the job for which we are manufacturing.  We do not want our item master to get out of hand; so, we reuse item numbers whenever possible.  For example, we will order a door to one job that requires right handed or left handed entry, slightly different hardware and different colors.  The costs difference in the doors is $0, but the cost in customer satisfaction if the wrong door goes to