Oh Sweet Mercy. Glad I finally started digging through Sonic Heroes E3 Gamecube prototype.

Some early level textures, Dreamcast source files, and more.

Bingo Highway has two test textures here.

Bullet Station originally had metal barrels, while the final uses wood barrels.

Egg Fleet has four textures, non in the final.

Then there's the early level .bsp meshes and objects .dff models.

en_element.one is also in here. Same as Xbox version. It is indeed Gamecube format.