Here is a hack which changes all the track layouts, some of the graphics, title screen, and also the drivers.
Super Mario Kart (Japan) (Rev 0A).sfc - NOINTRO
CRC32: C8002453
MD5: F7AFA112D7EC1D532636703E4B02700A
SHA-1: CBB853BF911255C1D8EB27CD34FC7855A0DDA218
SHA-256: C04F517C2675D7A8F3498D958F097443DFAA0E66606C69C59B58A915B3454973