Oil Pump Mounting Bolts?

it's no "biggie"...the rub is a grade 5 if stressed will bend or deform but hold together.A grade 8 being harder is more brittle and if pushed beyond it's limit will snap and fail.That is why suspension fasteners are built bigger for strength but remain grade 5.You always want to replace the fastener not the part.
unless you really know your stuff i'd stick with what the factory used.