After seeing what Chuck had to do to get some of those panels to fit I can understand the frustration a lot of people have with some panels.A few of them do leave a lot to be desired.
But also remember these trucks were pretty much hand built in the days before computer controlled laser cutters and robots.I've got a photo of the AD cabs being assembled and it was really nothing more than some jigs with a worker hand fitting the panels.There was probably a lot of trimming,tweaking,and cheating in the assembly,especially with the foreman breathing down your neck "To Get 'Em Out Of Here". If you look at old cab assembly blueprints you'll find a lot of tolerances in the 1/8 to 3/16 range. Go either way and you're talking almost 1/2" combined plus or minus. Throw in 50 years of bad roads, rust,abuse,and misalignment and it would be impossible to make a panel that fits every truck like a charm.
I'm not saying that there isn't a lot of room for improvement,but to expect a Made in Taiwan panel that was copied off of one truck to fit exactly perfect on every truck out there is never going to happen.