Researching the 1930's ones that I might be interested in:
4321: Lined with Great Crest Western: Built 6/13, Steam pipes 2/33, Withdrawn 9/37 (Wheels and motion used for Grange/Manor)
5350: Unlined Great Western: Built 7/18, front buffer beam weight added 1/28, removed 8/44 (during which time she was numbered 8350), Steam pipes 12/45, Withdrawn 12/59
4377: Shirt button: Built 12/15, Steam pipes 9/45, Withdrawn 1/59
4321 would not still be in that livery in the 30's, I'm 99% sure.
5350 must not have outside steam pipes and would have to be renumbered to one without the bufferbeam weight, in the same or similar Lot, without outside steam pipes. Say, 5349 or 5371?
4377 would work as long as the model doesn't have steam pipes (or they can be removed). Shame about the roundel, though.
Just thinking aloud.