Use a fascia panel something like this http://www.ebay.co.uk/itm/FP-06-00-P-BMW-5-SERIES-E39-1996-2003-PIANO-BLACK-FASCIA-FACIA-PANEL-ADAPTOR-/150903751682?pt=UK_CarsParts_Vehicles_CarParts_SM&fits=Car+Make%3ABMW%7CModel%3AX5&hash=item2322908402 and then you can fit any single din radio you like :)