What Were General Motors' Body Platforms in the Early 1950s?

The truth might be found buried someplace in General Motors' archives.  But the available information I am about to cite is inconsistent.  It has to do with General Motors' three basic body platforms used in the early 1950s.  They were the A-body, on Chevrolets and Pontiacs mostly, the C-body, found on Cadillacs and upscale Buicks, and the B-body for intermediate models in GM's hierarchy.  There were some exceptions, of course: for example, senior Oldsmobiles used C-bodies until the 1952 model year, then reverted to B-bodies.

In this post, I referenced an article in Special-Interest Autos magazine issue #39 titled "Body Politics" by Richard Howard Stout.  It was fascinating to me because it showed the various length and basic style permutations General Motors was able to attain for its most expensive car models.

But there was one potential problem.  Stout seems to have been dealing with C-body variations, yet he calls them B and C bodies.  His B-body is a shorter one than what he calls the C-body.  The links above as well as other reference material in my possession identify a different platform as the true GM B-body.

These cases are illustrated below.  Images are for Buicks and Oldsmobiles from model years 1950 and 1951.  For comparison purposes, all are four-door sedans.

Gallery

1951 Oldsmobile 88 - car-for-sale photos
Entry-level Oldsmobile 88s were given GM's A-body

The hood is fairly long and the rear fender is distinct.

The C-pillar is wide, while the backlight window is small compared to those on more expensive GM models.  Aside from the lure of its "Rocket V-8" motor, potential buyers might well have considered buying a straight-eight Pontiac Chieftain with the same body at the same price.

1951 Buick Special - Mecum auction photos
This is the GM B-body introduced for the 1951 model year and found on Buick Specials and Oldsmobile's Super 88 line.

The fenderline features an indicated-but-not-distinct rear fender.  Four-door sedans such as this were four-window affairs.  The hood is short, even though all 1951 Buicks had inline eight cylinder motors.

The backlight is panoramic, unlike that on A-body cars.

1950 Oldsmobile 98 - car-for-sale photos
This Oldsmobile has the lesser C-body.  Though Stout called this a B-body.

The passenger greenhouse is a four-window style with a thick C-pillar.  The hood is long.

The fenderline is dropped lower than on the previously shown designs.

1950 Buick Roadmaster - Mecum photos
This long-wheelbase top-of-the-line Buick has what Stout called the C-body.

A number of sub-surface body panels are the same as on the Oldsmobile 98.  But the windshield and six-window passenger greenhouse differ.

The fenderline is dropped, but not quite the same shape as the 98's.  Note that the rear beltline below the backlight is the same as the 98's, as is the central backlight panel.  In spite of many differences, some shared exterior components with the shorter C-body can be found.
Another thought.  The General Motors C-body shown above appeared for the 1950 model year, but the B-body came a year later, 1951.  So it's possible that Stout focused on the C concept when the 1941-1950 B-body was still in production, though in phase-out mode.  That might have meant that the shorter C-body might have been called the B-body by C-body engineers and stylists who were not particularly concerned about the upcoming actual B-body.