There was no 1.4 ever released, it was only used as boot ROM for the Superkickstart machines (like yours). You'll need to put a Kick2.x or 3.x image where the boot ROM expects it; the A3k floppy set has some tool to read it from a Superkick disk, but you can use any image - A3k version needed.
I'm a bit in a hurry (going to work), hope that puts you on the right trail. ;-)