On the main feed wires to pdc should the black wire test as a ground. I get no volt reading between it and the red wire. Also I get no continuity between the black and frame.

 

That's as it should be, red is the battery connection, black is the + from the alternator. There's a 120 or 140A fuse between them, if you read voltage between the red and blue the fuse is blown and your truck runs on battery only.
(Happens a lot if you touch the right spot on the alternator with an oil filter wrench...you see the spark and run for a fuse)