Turns out you CAN trade with legit copies of Soul Silver while playing Storm Silver on a hacked 3ds 🤘🏻hope this is useful to someone. : r/PokemonROMhacks
POKEMON SOUL SILVER VERSION NINTENDO DS CIB AUTHENTIC 3DS 2DS XL LITE DSI NDSL | eBay
Pokemon: SoulSilver (Nintendo 3DS, 2009) - Japanese Version | eBay
Pokemon SoulSilver and Diamond on a Nintendo 3DS XL - YouTube