jnast ina rotary

so i'm doing an engine swap in my fc. i'm not putting a rotary in it and i have to remove my engine harness from the ecu. but i need some main functions of the body harness which also connects to my ecu.

so here's my questoin. is it possible to disconnect the engine harness fromt he ecu and leave my body harness connected and still get the main functions out of it? such as tail lights. head lights. turn signals. heater controls. ect????

if not what kind of alternative option am i going to have to go with?
(such as direct power to certain wires in my body harnes?? toggles switches??)

any kind of information would help out greatly.

thanks