stinking water neck driving me crazy

One thing I try to do is make sure the water outlet is the same material as the intake it's being bolted to, helps prevent leaks later on from the different expansion rates of the metals (iron vs. aluminum for example). All the other suggestions have been good, I've had success using a gasket and a thin layer of that special grey RTV on both sides of the gasket; put thread sealant on the bolts and make sure they don't bottom out, then tighten it down "half-snug" and wait a couple hours for the RTV to set then torque them down fully.