Suggestions on maintaining custom parts within JDE, specifically as it relates to P4105

Our organization currently manage custom parts within the AS400.  We are working on an initiative to bring the custom effort into JDE.  There are several components associated with this effort:

1) the parent part is purchased

2) the purchased part needs to be included on a parts list which will be issued to a work order

3) the end product resulting from the completed work order will be associated with a sales order

Requirements:

1) both the purchase and inventory/sales component need to be actual cost.   Note:  For the manufactured component the 09 (Manufactured Last Cost) will work; however the set up of the purchase component is not clear to me.  In most cases the item will be purchased and issued to a work order; however there are cases where the supplier will send increments of the purchased component and an customer order is not created until all purchased components have been received.  How can we set up the purchased component and ensure on hand quantities are not revalued using average cost.  Again the purchase and manufactured component needs to be maintained at all levels using