The original manuscript clearly reads said. There is some noise surrounding the word said; moreover, the ascender for the d of said is smeared. Even so, there is no sign in 𝓞 that said was corrected to sayeth (or saith). When the text was copied from 𝓞 into 𝓟, said was changed to saith (spelled as sayeth). The historical present-tense saith is expected here in verse 7 because of the surrounding occurrences of saith in the original text:
Only in verse 7 do we have said in the earliest text (the original manuscript). The 1830 compositor, probably as a result of proofing against 𝓞, restored the original past-tense said here in verse 7, although he probably set saith originally.
This variation between saith and said was removed by Joseph Smith in his editing for the 1837 edition (five out of the six changes from saith to said are marked in 𝓟); thus in the current LDS and RLDS texts, this passage consistently reads as said. The critical text will, however, have said in verse 7 but saith in verses 2–6 and 8. Such mixtures in tense for narrative discourse can be found elsewhere in the text; for another narrative where the historical present-tense saith dominates but said still occurs, see the discussion under Alma 11:36.
Summary: Maintain in Alma 45:7 the unique instance of said in the earliest text; restore the six instances of original historical present-tense saith elsewhere in this narrative (in verses 2–6 and in verse 8).