I changed out the V-mount plate on my Zephyr to AB. It is just a basic +/- pair of wires. Just unscrew the old plate, un-solder the leads, then solder them to the new plate (double check the polarity) and screw the new plate back down. I imagine it's just as simple on the Flyer LE, but sorry I don't know about the holes.
On Zephyr, the battery bracket plate has holes for both V and AB mounts already, but mine had pre-sunk nuts for only V-mount. I bought some lock-nuts and used the screws that came with the AB plate to secure it.