Some updates here.
As Nico said, there are four versions of Arcade:
> Arcade original leak (sometimes called "Arcade++"), 25+ textures, 230 sectors
Its file format is similar to 3Dfx / D3D5 Pod ("BV4"), but incompatible due to small layout changes: the difficulty / direction chunks are not offset (apparently useless since Arcade only provided FORWARD/HARD games), and an additional background parameter was added.
> Arcade+, 24+ textures, 79 sectors
90s hack working with D3D5 Pod. Heavily reduced version (fewer sectors, no texture or model animations, no dynamic objects) to accomodate the game's memory manager not providing enough blocks to load it otherwise.
> Arcade, 20+ textures, 73 sectors
90s hack working with D3D5 and 3Dfx Pod. Further reduced the texture count as the 3Dfx texture manager does not allocate enough texture slots otherwise, causing textures to overwrite each other.
> Arcade-, 20+ textures, 76 sectors
90s hack working with D3D5 and 3Dfx Pod. Possibly created for weaker hardware.
Interestingly, all 90s hacks were given a working Reverse and Easy/Normal mode which do not exist in the original leak. It also replaces the AI names with ones of popular players active at the time.
There is now a hack available (increasing the memory manager block count as required), together with a faithful port of Arcade(++) to fully load it with all models, textures, animations, dynamic objects, and including the Reverse/Difficulty enhancements of the 90s hack. You can find links on the POD Discord at discord.gg/zJ9bWGkDvT .
In the 3dfx versions, you must enter "MIPMAP" in the main menu screen before starting the race as the textures will otherwise look glitchy - a fix enabling this by default is also available on the Discord.
Here's a video of it.