Well, because I wouldn't be able to sleep well thinking about it, and because it's still 65 degrees outside at 2:30 in the morning, I pulled the front off and got down to what I think is the problem.

My new water pump (GMB branded) is not EXACTLY the same as my old one. The bolt hole that goes through the water pump to hold the accessory mount onto the engine block must be a little too thick. This is causing the accessory mount not to sit flush with all the other mounting spots. So when it's torqued down, the accessory mount becomes contorted, and the oil filler bracket doesn't fit.

There is just this tiny nub (like 1mm or less) on the face of the water pump.. I'm going to see if I can file it down..... but, I will do that after some hours of sleep.