The 4th Fighter Group transferred from the three Eagle Squadrons of the RAF to the 8th USAAF, still equipped with the Spitfire MkV. They re-equipped with the P-47, then got the P-51 in 1944.
All 8th AF P-47 Groups in ETO re-equipped with the P-51 by January 1945, except the 56th FG, as did some P-38 Groups, such as 20th FG.