To make sure we are on the same page, I take it you want get rid of Sprint car menu icon and replace it with an Axel menu icon for car 47?

If this is correct, then you need to unpack carpack 1 or carpack 3 ( depending on which carpack you are going to load before loading axel bfs ) and under the \data\menu folder look for car_iconstest.dds file.
It look like this in Photoshop. If have Photoshop and it won't load a dds file, then you will need to get the dds plugin for Photoshop.

The second car in the pic is car 47. You will need to blacken out the Sprint car and take an in game pic of the Axel and load it into Photoshop and crop the area around the Axel and and then paint that area around the Axel black ( 0,0,0 - pure black ), so you just see the Axel car.
Now need to shrink your Axel pic down to the size of the cars in car_iconstest.dds pic and then paste Axel car into the spot where the Sprint car was before you blacken out the Sprint car.
Now if happy how car_iconstest.dds looks, save file and then put car_iconstest.dds in your unpacked axel.bfs file under the
\data\menu folder so new car_iconstest.dds will over write old car_iconstest.dds file. Now pack your files backup into a new axel.bfs file.
Shadow did 140 these custom cars for the 3 carpacks we did. Thanks again Shadow for all your hard work you did on the carpacks.
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About the tires, there a
\data\cars\shared folder that has the tire files for the 4 cars. The Axel uses the tire_47 files. You can delete the other 6 tire files.
Heddly, does Nokikana need to keep the other 31 files, minus the tire files, in the shared folder? Won't some them files effect carpack 1 or 3 cars 46, 48 and 51? Or will they be ignore since there no car.bgm file for Motter's car 46, 48 and 51 since Nokikana has delete them from his axel.bfs?