Freakin' water outlet won't seal!

When I put the motor in I put in the reducer that was with the motor instead of a thermostat and it sealed just fine. When I redid the intake, I decided to put in a 160 degree thermostat. I used a gasket and 3M weatherstrip adhesive like I always do and it seeped coolant. I took it off and cleaned it off well, checked the outlet with a level, used our very good Motorcraft RTV and a gasket and reinstalled it. It leaked again. I took it off last night, went through the routine again, used more RTV than I normally would and reinstalled it. I didn't fill it until this morning so it could set up. I bled the air, watched the thermostat open, and went for a drive. The dang thing is leaking again. WTF? I am going to block sand the intake side next. Any ideas?