When you said '0' pressure my first thought was that you may have main bearing troubles but the lack of oil in the pan and no leaks can only mean that it is going out the tail pipe. Sometimes it is difficult to see the blue smoke in your mirror as you are driving. Have someong follow you as you put your rig through the gears. One problem that I have run across with some of the 70's era Ford motors was bad valve guides. On compression as in low gear down a hill, oil would be pumped through the guides and into the cylinders and burned. In a word, that SUCKED.

Good Luck