A BCM 400 is a a hardware upgrade to 450 release 'x'. The software upgrade is only good to upgrade 450r1 to 450r5 or 450r6. There's no method of upgrading a 4.0 bcm400/200, other than collect the data using the DMM tool, upgrade the hardware (new base function tray, new fan, new chassis interface card, new SATA hard disk). Once hardware upgraded, then you'd use DMM to repopulate the configuration and mailbox data etc on the BCM.
Plus of course you need an auth code to regenerate the 4.0 keycode against 450 release 'x'.