You probably know that the Squadron Code was AR, but as both Lancs were lost on operations to Hannover, the individual aircraft code does not seem to have been recorded.
Perhaps contacting the RAF Museum at Hendon asking for all available information and Loss Reports might throw up the missing info.
Two of the crew of JA680, lost 27/28 Sept '43, were RAAF and it may be possible for you to contact the Australian MoD and apply for the crew records. It has been known for those files to contain more information than the RAF files, and on other crew members.
Have you checked this site
aircraft_record?
460 Squadron Lancaster Mk III. Serial Number: JA861. Aircraft Code: AR-? Operation: Hannover. 27th/28th September 1943. JA861 was delivered to 460 Sqdn 10 July 43. Took part in Key Operations to Turin on 12/13 Jul 43; Hamburg 24/25 Jul 43; Hamburg 2/3 Aug 43; Peenemunde 17/18 Aug 43; Berlin 3/4 Sep 43; Mannheim 23/24 Sep 43; Hannover 27/28 Sep 43. When lost, this aircraft had a total of 161 hours. JA861 was one of two 460 Sqdn Lancasters lost on this operation. Airborne 19:39 27 Sep 43 from Binbrook. Crashed in the target area. All were buried 4 Oct 43 in Hannover War Cemetery. F/Sgt M. Dargie RAAF KIA; Sgt A.M. Barnes KIA; F/O S.V. Cole RAAF KIA; F/Sgt C.K. Bolger KIA; Sgt F. Whiteside KIA; Sgt W. Thornhill KIA; and Sgt C. Jeffcock KIA.
460 Squadron Lancaster Mk III. Serial Number: JA680. Aircraft Code: AR-? Operation: Hannover. 27th/28th September 1943. JA680 was delivered to 460 Sqdn 19 Jun 43. Took part in Key Operations to Cologne 3/4 Jul 43; Turin 12/13 Jul 43; Hamburg 24/25 Jul 43; Hamburg 27/28 Jul 43; Hamburg 2/3 Aug 43; Peenemunde 17/18 Aug 43; Berlin 3/4 Sep 43; Mannheim 23/24 Sep 43; Hannover 27/28 Sep 43, when crashed on return leg. When lost, this aircraft had a total of 204 hours. JA680 was one of two 460 Sqdn Lancasters lost on this operation. Airborne 19:49 27 Sep 43 from Binbrook. While returning to base the navigational aids failed due heavy airframe icing. At 03:20 28 Sep 43 an emergency wheels-up landing was accomplished near Aldeburgh, 7 miles SSE of Hornsea, Yorkshire. F/Sgt P.A. Crosby RAAF; F/Sgt L.H. Chapman; Sgt M.H. Bender; F/Sgt C. Billett RAAF; F/Sgt C.B. Suffren RAAF; P/O L.W. Robb RAAF; Sgt C.F. Hodge RAAF. This crew were subsequently lost on a Gardening sortie 9/10 Apr 44. See: ME663.
These aren't the only 2 unidentified 460 aircraft, is there any specific reason you have selected just these?