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.

Retorque as above and pressure test again.
Then if still gushing water;
Empty the pan and leave the plug out.
Take the plugs out.
Then pressurize the cooling system with air on top of the water, at about 4psi but not more than 10>12. Then I would check each hole with the piston at the bottom, to see where the water comes out.
Hopefully the cylinders remain dry.
Hopefully the water comes out the pan.
After that, it's probably a cheap fix, and the bases have already been covered in earlier posts.
When the water is finished coming out, escaping air will be your friend, just follow the sound.