best path really, will take you less time then. While bodywork is off can split engine and box easily, mount box on rubbers, angle it flat using spirit level and prop to correct height, cut engine mounts, mate up again and weld in engine mounts again making sure they're levelled correctly
May not even need to take them apart tbh, with engine crane can lift up box and engine in one, drop box into mounts and bolt up then lower engine into its correct place