Heres a starting sample without physics.
Physics could be done with regular dark basic commands or from someones plugin commands.
Also I would think a basic track would be needed to plan out the physics for it.
Hopefully it helps.
Attached zip file.
Updated it a little and took away the 4 frames from each car.
As far as editing the bitmaps,I would not because they are yours.
I really don't do sprites after doing a few in a paint progam awhile back lol.But putting them in rows across all on the same bmp I think would be better and not as much image loading.Your sprites are cool btw.Had fun playing with your cars

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I have my eye on ProMotion for future sprites I might try to make.