The four big ticket items in an EV conversion are the motor, the controller, the batteries, and the battery charger. Then there is all the bits and pieces required to adapt those to the vehicle and to make them work together and you also need to consider bits required to make the vehicle systems work that were dependant on the ICE. So we have adaptor plates and couplings to connect the motor to the gearbox and motor mounts, battery racks, and boxes. The systems required to tie the main electrical components together include your high voltage cabling, contactors, circuit breakers, fuses, and connectors then there is the low voltage relays for you interlocks and ignition switch etc. The systems that were dependant on the ICE include the heater/air conditioning, power steering, vacuum for the brake assist, and charging for the accessory battery. Your choices on how to make those systems independant will determine the components required.