Hi Peter
I have found a couple of websites where Lt. William P. Rowles is mentioned. The first was on the 8th Air Force 'Littlefriends' website which deals with the Fighter Groups connected to the 8th AF.
http://www.littlefriends.co.uk/ Just click on the 4th FG and then type in Rowles.
This shows that he was with the 335th FS, 4th FG, and also has details of an aircraft that he flew. This was a P-47D Thunderbolt serial number 42-75112 and coded WD - Z. No name is listed for this aircraft.
The second website is the 'Aviation Archaeological Investigation & Research', which lists Lt. Rowles being involved in an accident at Shaw Field, South Carolina on May 14th 1943. Here are the details:
http://www.aviationarchaeology.com/src/dbapi.asp?Pilot=rowles%2C+william+&Submit7=Go You can get a copy of the 'Accident Report' from either the 'AAIR' website, which does charge, or from the Air Force Historical Research Agency (AFHRA) at Maxwell Air Force Base in Alabama. This is free from AFHRA, but will take longer. Here are the details for AFHRA:
http://afhra.maxwell.af.mil/ Just scroll down until you come to 'inquiries', where you can e-mail your request to them.
Hope this helps you.
Regards
Chris.