remove exhaust manifold bolts

1970 Plymouth Valiant, 318

Just discovered coolant leaking from one of the studs. However, the previous owner used bolts instead of studs on the ends.
Will this give me any advantage when removing them? (buying Kroil tonight)
Should I replace them with the proper studs?
I like to use new hardware, is there a manifold bolt set that is popular to use?
Thanks
Danny