the hole behind the dist. is supposed to be for the oil pressure sender. They say the one above the filter isn't full pressure, my block didn't have the other one though so I used the filter hole. The water temp sender is a threaded hole right next to the water neck in the front. A brass plug with a temp sender on it will thread into that sucker just like a heater hose fitting would, which is on the other side, I doubt it matters which one you use for what.
This info is all based on my big block so small blocks could be slightly different.