In trophy truck, it's purely preference. I can only think of a couple classes that really dictate carb vs. EFI and actually it's not even dictating that. It's more like you HAVE to run an ecotec, or you HAVE to run a crate LS setup supplied by turnkey or you HAVE to run a factory offered option for that specfic vehicle so sometimes that'll dictate it but in TT, anything goes. The jist of the rules in that class is the tires need to have fenders over them, it should sorta look like a truck and the grill needs to match the motor make. Beyond that, it's almost 100% wide open other then general safety requirements.