Water in oil after rebuild - looking for guidance

As for intake bolts
3/8ths coarse are about 25>30 ftlbs
5/16ths coarse are 18>22
The only bolts close to 12 on your engine, are the 1/4-20 oil pan bolts which are 15
I wonder if you have foot-pounds confused with something else.
The Magnums have a funky multiple step torque procedure from the factory where you go 72 inch-pounds a few times and then you go 12 foot-lbs twice, all in their little sequence. The bolts and gaskets are not designed from the factory for more torque.

Which reminds me, there was supposedly a bulletin back in the early Magnum days about too much torque pulling the corners of the manifold up causing coolant leaks. Never seen it myself though.