Originally posted by Greenneck: I know this is a long shot but my 16-50 needs the conversion and the lens is not really worth the shipping costs to send it to anyone on the forum.
There is also some discussion of the SDM to screw drive conversion here:
How to deactivate SDM and allow for screw drive autofocus with DA* 16-50mm f/2.8 - PentaxForums.com