Job is done.
We removed the top half of the suspension on the passenger side.
We drilled a hole at the right place in the inner panel/tower.
We then used a long drill bit to drill it out and then an extended tap to tap the threads.
We will weld up the hole and the put the suspension back in next
I would remove the heads. Why make it harder for yourself. A couple gaskets added to the price isn't much. I would pull the motor if you don't know much about it condition wise.