1 It is probebly a rusted out timimg cover, I have found many over the years that look fine but are pin holed on the inside, And as you are in the south, there is a good chanch someone ran straight water in the car at one piont, and that always increases the internal corrosion. So I would pull the timing cover and check it out, especially if you say you know the intake is good.
2 Sorry I am in Michigan, can't help you much there.
3 the ground for the tail light harness in my 69 in betwen the tail lights screwd to the trunk floor, also remember that each light socket has a individual ground that makes contact with the tail light assembly when you install the socket. I would first check to see that you are getting 12 volts to the sockets, and then check and clean the harness and all individual socket grounds and see what hapens.
