No, it is not from body twist. It is from the lead separating from the metal. This is joint where the windshield pillar is welded to the cowl. The factory did some gobby welds, then covered up the mess with lead. Which would have lasted had they actually neutralized the acid used to tin before leading the seam. You will see this same issue at the rocker to quarter joint and the roof pillar joint on painted roof cars (vinyl top cars got bondo, yes bondo, from the factory). I can assure you that body twist is almost a non issue in a 68-70 Mopar B body. You want to see body twist, look at the GM full frame cars. unibody cars are so much more rigid than any body on frame design. The crack by the door also has zero to do with body twist. It is from the stress of the door being slammed a thousand times, and road vibration adding to the cracking.