The NOAA's Herc(s) are not structurally modified in any way. The only mods are associated with the fitted sensor equipment.
If you think about it, why would flying through a hurricane be any different to any other weather phenomenon? The windspeeds you will encounter are no more fierce than in the average jetstream, and updraughts are considerably less intense than an average CB. What makes hurricanes so destructive is that these windspeeds reach ground level.
16B