The Langley Memorial Aeronautical Laboratory reported in April 1947 on spin tunnel testing on a swept wing model of a P-47. The modifications were made to an existing Langley spin tunnel model, and it appears that the design was a NACA-Langley design rather than a Republic Aircraft design. By 1947, a swept wing piston engined aircraft was already an anachronism… unless there was some thought of making a research vehicle from a P-47 (as was done with the P-63 to make the L-39), by this time any swept wing fighter design would have had turbojet engines. Most likely the idea was to simply represent a generic swept wing aircraft, using on-hand resources.
The horizontal stabilizer was tested in two positions…. the P-47 original, and moved upwards and slightly forwards.