Water pump threads SBF

I've removed my water pump from the engine block and am moving to an electrical one in the front bay. I need to know the thread used on the bolts that held the water pump in place on the block. These bolts used either screw into the timing cover or into the block through a hole in the timing cover.

I got coupling made to take the water into the block and I need different length bolts to fix them to the block. I measured the diameter of the old ones, 0.309"/7.86mm (which is guess is 0.3125" or 5/16). But which is the thread used on these, anyone know off hand? K
 
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