Half of block not firing

This does not make much sense because most manifolds are 180*, meaning, something like a leak normally will affect every other cylinder, not an entire bank.

What I'd try: You need to SHORT plug wires, not pull them, "if that is what you did." This is because of spark crossfire on a disconnected wire position. What I used to do, is to loosen the dist. boots and wires so you can easily pull them, with an insulated pair of fuse pullers, etc, and then in the other hand, hold a grounded probe, and as you extract a wire, insert the grounded probe into the dist. tower. You should be able to see what ones are firing or not

Did you cross tighten the manifold bolts?

And is this in fact a 180 design, as opposed to something like a Torker/ or 360 design?