Here the 1906 LDS large-print edition reads unto rather than until for the phrase “even down until the time that ye shall receive these things”. Either reading is theoretically possible here, so we follow the earliest reading, until. The 1906 edition never served as a copytext, so the reading with unto was never passed on to any subsequent LDS edition. The use of until is consistent with usage elsewhere in the text: there are 14 instances of “until the time” in the earliest text but none of “unto the time”. For two other cases where the prepositions unto and until have been mixed up in the history of the text, see under Mosiah 17:10.
Summary: Maintain in Moroni 10:3 the preposition until in the expression “even down until the time that ye shall receive these things” (the reading of the earliest extant text).