A possible emendation for loading is lading. Both loading and lading have the same etymological source, but loading is the more common word in English. One could possibly consider loading in the original manuscript to be an error on the part of the scribe, replacing the less familiar term lading with the much more frequent loading. On the other hand, according to the Oxford English Dictionary (see definition 1a), loading is perfectly acceptable as a term for the cargo of a ship.
In the King James Version, we have two occurrences of lading. It occurs only once as a noun:
The other occurrence of lading is a verbal form:
The word loading never occurs in the King James Bible, and it occurs only once in the Book of Mormon (here in 1 Nephi 18:6). But lading itself is infrequent in the King James Bible, so there is no strong evidence for replacing loading with lading in the Book of Mormon text.
Summary: Maintain loading in 1 Nephi 18:6 instead of lading, its etymologically related alternative; there is no textual evidence that loading is a mistake for lading.