I am starting to put my engine together after the damage a nut caused to # 5 piston. My engine is bored 0.060 over size. How important is it to find a head gasket that is 0.060 over?

 

most stock gaskets are made to accommodate standard over bore sizes, make sure when you lay it on the block that the fire ring sits where it should be,
for a example i recently assembled a 66 289 that was bored to 060, had zero issues using a standard victor gasket kit. take your time double check every fit