Here the original text (as recorded in 𝓟) read “if thou art spared and I should perish”. The 1830 typesetter replaced the conditional modal should with the future shall, perhaps intentionally (for several other cases where he replaced should with shall, see the list under 3 Nephi 1:8). Here in Moroni 9:24, the 1908 RLDS edition restored the original should by reference to 𝓟. Earlier, the 1906 LDS edition replaced I shall with should I but without reference to 𝓟. Thus the 1906 edition reads “if thou art spared and should I perish”, a mixture of two different ways of expressing conditionality (first, by means of an if- clause and then by inverting the subject-verb word order). The 1907 LDS vest-pocket edition also followed the 1906 reading with its use of should but restored the normal subject-verb word order, thus unintentionally ending up with the original reading (“if thou art spared and I should perish”). However, neither the 1906 or 1907 editions served as copytext for any subsequent LDS edition; thus the secondary 1830 reading has been maintained in the LDS text.
Summary: Restore the conditional modal should in Moroni 9:24 (“and I should perish”), the reading of 𝓟 (the earliest extant textual source).