There were only 2 types of seat, the wooden Shick-Johnson used on the first 800 Bs and the first 100Cs built, serialed 43-12093 to 12492 and 43-6313 to 6712 for the Bs, and 42-102979 to 103078. The Warren McArthur was used on subsequent planes. Information provided by the Part Catalog manual. However, NAA drawing 102-53009, while confirming information regarding the B model, says that all Cs received the Warren McArthur seat.
You will find ties for the RAF S/N scrolling down those pages
http://www.joebaugher.com/usaf_serials/1943_2.html
http://www.joebaugher.com/usaf_serials/1942_5.html
Laurent