Cracked Spar

Univair to the rescue, once again. Service Memo 64 and Service Assembly 24 address this repair.

During my first annual, my mechanic has found an old 1" spar crack which was previously stop drilled. The crack is on the top of the left wing rear spar, 6 to 8" from the wing attachment. The plane is a 415C, S/N 3718. Is there an approved repair for this crack? Thanks for any help.