I'd be interested to see the finish on the inside of a well preserved motor, but don't believe it would have ever matched completely with the outside due to shielding from the current during the plating process When parts are plated the inside surface will almost always be less bright that the exterior. The way to try and avoid this would be to use a conforming anode, more costly and time consuming, a method I highly doubt Chrysler would have imposed as a requirement.

As for brightness, there are several factors that play into this, as someone pointed out, the quality of the substraight prior to plating plays a factor and since these were new at the time of build I suspect the finish pretty nice but certainly not polished to remove small imperfections in the surface.

Another factor affecting surface finish is the use of brightens within the plating bath. Brighteners act as a leveler to the material being deposited, the smoother the deposit the more shine to the finished product. Brighteners are not all created equal, some performing better than others and the amount used (and maintained) in the bath plays a factor as well.

While I too have my own opinion of level of correctness I can say theres a scale or range that should be considered plausible as I'm sure that if able to inspect a few original motors done in the day, variation could be seen.