The 728th Bombardment Squadron (Heavy) was one of four squadrons assigned to the 452d Bombardment Group (Heavy). The 452d was an element of the 45th Bombardment Wing of the 8th Air Force. The group was based at Deopham Green, England. Government records regarding "Buffagator" would take forever to locate. Fortunately, the 8th Air Force Association still has a relatively large and active membership. I can provide you with unit histories of the squadron and group. I can also put you in touch with a former member of the 452d.
I just happened to have info on the group from research I did on First Lieutenant Donald J. Gott and Second Lieutenant William E. Metzger, Jr. a while back. They were, respectively, pilot and co-pilot of B-17 #42-97904 R, "Lady Janet", which went down during a raid on the railroad marshalling yards at Saarbrucken, Germany on 9 November 1944. They were members of the group's 729th BS(H) and were posthumously awarded the Medal of Honor for their actions in the Saarbrucken raid.
As an aside, your Grandpa's plane's name reminds me of the old story about the three guys debating as to the world's most vicious animal. One suggested a leopard. The second suggested the Brahma Bull. The third proposed the Hippogater, an animal with the head of a hippopotamus at one end and that of an alligator at the other. The first two inquired as to how it relieved itself, inasmuch as it had a head on each end. The third guy responded, "It doesn't - that's why it's so vicious!"