For what route? If you wanted them streamlined, then it'll have to be for a route set before the BR as all examples where de-streamlined by Nationalisation. 6229 is the only example of the Duchess Coronation in preservation that is streamlined but she has never ran under her own power whilst streamlined..
LMS days of course i am talking about 6220 coronation that did ran under her own steam in 1937 built in 1911
That route is set in 1958 so you wouldn't get any of the streamlined variants as (like I've said) they all had their streamlining removed between 1946 and 1949
