Help in Differences between 1957 Roadmaster Models

I would like to know if anyone can steer me to material that would make clear the real differences between the 1957 Roadmaster Coupe Models: 75R, 76R, & 76A respectively?

Of course this would be no doubt the differences available regarding standard options vs. optional options and appearance packages between the three model designations for 1957.

But I would like to know. For instance I have found that the 76R had the split rear 3-piece window option while the 76A had just a one piece like the super models.

However, the total production numbers for all three were lower than the comparable convertibles for that model designation. In the low to mid 2,000's.

At any rate I suspect the interior options which were available were different and I would like to find out just what they were. Having a little trouble finding specific information.

Dave