I've never done it, but from what I've read and been told the 'swap' from single to double trigger (or vice versa) on an MS is rather simple, though perhaps not on the 'Takedown Model' due to the TD having a different trigger plate which incorporates the TD release lever. If true, the question becomes one of whether the 'prewar' and 'postwar' assemblies interchange with one another.

Perhaps these images will be of use?

M1900, single trigger

'Prewar' MS, double trigger

Detail of 1954 Stoeger catalog. It appears that the 'postwar' MS has omitted the roller and pin from the 'trigger lever' (as identified in parts list of 1939 Stoeger) while the single trigger gained a 'regulating screw'.

Double set trigger parts, 1939 Stoeger

Detail from 1961 Stoeger (same image used in 1957).

Stoeger, 1954

Stoeger, 1961