Here we have an initial error in 𝓟 where Oliver Cowdery accidentally wrote ye instead of the correct we. He was undoubtedly prompted by the occurrence of ye in the preceding clause (“that ye may have that precious gift of eternal life”). Virtually immediately Oliver caught his error, crossing out the second ye and supralinearly inserting we (there is no change in the level of ink flow for the correction). The inclusive first-person plural pronoun we works much better here than ye.
Summary: Maintain the we in Helaman 5:8 (“which we have reason to suppose hath been given to our fathers”), the corrected reading in 𝓟 (the earliest extant source).