i haven't really had much luck, but here's what i've found so far:
Mario - 00
Luigi - 02
Bowser - 04
Peach - 06
DKjr - 08
Koopatroopa - 0A
Toad - 0C
Yoshi - 0E
Changes the first driver Code:
7E1712?? (Example: ?? to 04 for bowser)
the codes seam to work differently, code for the first driver changes kart AND palette, also Bowser stays #1 after the code is disabled.
Code for the second changes only kart, not palette, and kart changes back once code is disabled. (palette does change if race is restarted with code ON)
i searched player values in hex, but couldn't find them in any of the driver position orders (aka 08 06 0E ect)
so i dunno.
using the (E) version, though i could easily switch to (U) if need be.
using a debugger you could put a breakpoint at this RAM adress to find where it was taken from in the ROM
i've never done this so im unsure how its done, could anyone teach me? or help?