Engine block welding

[MS66]

This question is for the guys that have welded a broken outer starter bolt hole on a SBC. I need to hear from the welders that have experienced this, not an internet article on cast iron welding.
I have a small block 400 with a piece broken out of the outer starter bolt hole. I want to have it built up to machine it, then drill a new hole. What method of weld is the most effective to keep it from cracking? I have a new tube of NWL 99 nickel rods. I thought that was the go to fix but now I hear of heating it and mig welding it. I also see a different rod now, Muggy weld 77 rod. From Muggy website: "The 77 rods are softer than nickel rods, allowing them to stretch up to 300 percent more to prevent the base metal and weld from cracking."
Guys that race have said mig welding works. Anyone in here with experience welding blocks? TIA