User Exits for delivery number ranges , partner determination

I need to know two User exits for

1) Number Ranges for delivery document

EXIT_SAPLV50S_001 is this the tight exit to be used .

I need to set number ranges for delivery based on plant.

2) User Exit for Partner determination

I want to fetch the partners from the sales doc .

which does not happen in my case as delivery happens through projects systems and there is no link between sales order -> delivery -> billing

only link between del-> bill exists .

An element called the WBS can be used to get the appropriate sales order from delivery.

I thought the exit EXIT_SAPLV09A_004 would help but my colleague has a different opinion.

Any inputs / logic on the same appreciated