obd2 magnum swap?

ive been reading alot lately. my dad want efi with his magnum swap. we have the ecm and harness out of an 01 ram. ive read that obd2 requires a bcm to run. is this true? what exactly is the bcm? is it the fuse box under the hood? will i need to run any wires inside the car? what fuel pump will work? these are just a few of my questions. any insight is greatly appreciated, thank.