Generally, you would just copy the whole layer and enable just that recipe, which should do the trick. That's a saner way I personally use. Instructions on enabling it are in the README in the root of that repo I referred to above.
Now, theoretically, you should be able just to replace that 2.4.3 recipe indeed, but you say there's an error. Care to share the exact output? I guess it may be coming from one of the further .bbappend files or something.
