Cadillac: 89 Eldo water pump bolts

I have a question for the wizards - I have my great little Eldo out of
service right now because, as I installed a new water pump, I noticed
the three 15 mm bolts (as part of the array of 17 different nuts and
bolts used to secure the water pump) are two different lengths. One
bolt is 1/4 " longer than the other two. Some time ago I read a
forum comment on this exact item but I can’t find it to refer to. So,
my question is simple - can you tell me where these bolts go so I
don’t end up cracking the aluminum castings or something stupid like
that?...Tom ops: