Broke the rear stud/bolt thing off the rear of the thermostat housing and drilled and tapped it...metal shavings fell into that bolt hole while working...it that anything i should be worried about or is it sealed from everything else...thanks

I'd think there should just be metal shavings in the coolant - might cause a blockage in the radiator but that would be the smallest passage area so that would be the only place.

i think you are okay its just a bolt hole and no coolant leaks from the bolts. put antiseize on the bolts just in case it leaks again and the bolts rust.