Original text by jimbo390.
I also found a "maybe" beta mario emblem; Mario’s head in red with a "M" inside. Also, all kart models in the beta files have a strange emblem, sometime it’s a number and sometime it’s not…. Maybe it’s just for the position….
I’ll use the beta wario kart for example but it works with any kart.
For the karts, unpack KartModelMain.carc located in the data folder in the final rom After unpacking, in that file, go to the kart folder and find the wario folder Next, copy the kart_WR_b.nsbmd and .nsbtx files in the the "KartModelMenu/kart/wario" folder in the rom. Replace the others files and it will appear in the menu.
How to make it work in race:
Now decompress the file named "KartModelMainA.carc in the rom and get NarcExplorer. Open it and replace the same files that we replaced in the first step.
Depending on the kart you replaced, the tires can have the wrong size or the character position is too high. The next step is to make the tires fit with the kart (no need to do this for the beta yoshi kart). Get an hex editor and open the file "Kartoffsetdata.bin" in the "KartModelMenu" folder in the rom. Open the same file located in the unpacked KartModelMain.carc file. Now go to offset 00000e00 in both files and select from "00000e00″ to "00000edf" in the unpacked one. Copy the selection at the same place (00000e00) in the other file and save.
Now you have to to the same thing with the in-race file (the one in KartModelMainA.carc file).
Pack the rom and it should work.
For the emblems i don't know how to replace them for now because they are in the same texture file as the kart…. I can only view them with the model. But as soon as I find how to do the hack i'll post a tutorial.