Both the 30kwh and 40kwh packs use modules that are physically different from any of the 24kwh packs, so once you figure out how to install the modules and connect them to a CANBUS adapter and the car's high voltage cables, they don't differ that much from each other. The only setup so far that provides 40kwh of usable capacity to a formerly 24kwh Leaf is one that uses ALL of the battery-related electronics from the 40kwh car. That's my understanding, anyway. People have been using 30kwh modules in Vectrix VX-1 motorcycle/scooter conversions for a couple of years now, but that's much easier because they use fewer modules to produce the 146 or so volts a VX-1 needs, and they often use no BMS at all, except the one in the bike's charger.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.