Sorry Gerry nothing on 49 YH 39. The nearest was 49 YH 24 on 13/11/57 but that of course has no relationship to yours, but it does show my few catalogues only cover a tiny proportion of what was registered.
There were particular sale days, 2nd or 3rd day generally, with Jeeps in big batches. But there a few Army ones slotted in here & there. The RN & civil licensed Jeeps are not in batches but just here & there, no doubt reflecting the small numbers issued.