I bought the wrong water pump and need advice

[cerebus]

about a month ago I bought a water pump to replace my old one. I spoke to some board members and decided I should get a 73' style long water pump. So I went to part souce and bought the 73' pump (P929 is the model number) and I traded in my core for the stinking $3 rebate.

I broke my hand recently and havent had much time to wrench on this thing so it sat for a few weeks.

Now I got the new pump on and my alternator bracket doesnt fit. the metal around the bolt hole on the alternater bracket is just too big to fit on the back of the water pump.

I got frustrated and didnt want to start ordering parts blindly so I spoke to my mechanic. He said if I could get the core back he can figure out which pump I need.

So I went back to Part Source and tried to get my core back and it was sent away already. I cant get it back and I dont know what the part number on it is.

Any ideas on what I should do?

A) modify (grind) the parts to see if I can make them fit possibly making things worse
B) purchase new Alternator brackets blindly hoping they will fix my problem
C) take it to my mechanic and just pay for him to figure it out ( im trying to do this on a really low budget so I can afford other new parts )
D) ????