Bitter taste of defeat! So much coolant in the oil pan.

I was gonna say I never has issues with metal gaskets sealing up with a 1st gen Torker aluminum manifold on my old 351C, even for vacuum leaks.

OP, check the compression on the front 2 cylinders, but it may be the case where 1 or 2 of the timing cover bolts would hit a cylinder BELOW where the compression rings travel. I have not looked to see for sure if that is the case. So that test may not be foolproof. Hopefully it is just sealing issues.