I seem to recall you had most chance in a cleaned off T8, I 'm sure someone will know for sure!
XW175, back when it was a T2, did a bit of envelope expansion after XW174 had an early exit. Peak mach number, according to the FT summary, was sufficiently above M1 to be respectable for a "subsonic" jet. Downhill obviously, but not to an unreasonable extent. That would presumably have been a bare airframe. It doesn't have pylons on it today, but the U/F instrumentation pods aren't really optimised for high M fun. Goes pretty quick at sea-level* though
*plus a bit. Well one wouldn't want to scoop up any wave-tops would one?