Resolving mod conflicts and editing rewards file

i tried downloading a family wagon mod that seems to conflict with both the roofed family sedan and ultimate level 7 restoration mods. when i attempts to enable the file the error reads as follows: The mod "simpsons family wagon" conflicts with the following parts of the following mods: roofed family sedan file "sound/scripts/car-tune.spt and Ultimate level 7 restoration file "scripts/missions/rewards.mfk". it will not allow me to enable all of these at the same time and will not alllow me to set a load order. the wagon mod makes a point to state that i should make sure my rewards file has enough space for more rewards but i have found not a single shred of info on what this means or how to do it. as it stands i am completely lost and am unable to find any info to either help me make all of these work together or if they will not then what makes this the case.

The mods are incompatible because they modify the same file and there is no way to properly resolve such a conflict with the mods as-is.