John, I have been discovering the same thing on the '57 Desoto convert I'm working on. The engine is offset to the right on the front end, the back points to the left. I tried all of
possible combinations of front and rear motor mounts and found I couldn't get the engine parallel to the chassis. The rear crossmember is definately offset and will
fit the chassis 180 degrees. The park brake drum appears to be centered on the frame, but it sure looks strange. I knew that Chrysler offset the engines to the passenger side, but never noticed or realized that the package wasn't parallel. I have the powertrain on my project in running mode. There isn't any vibration that I can tell, even at around 3K rpm. Wonder if that is why Chrysler used the ball and trunnion joint. I've always heard that they were a better joint than the standard joint.