Jim R and Tinplate Tom
Thank you for clearing up my confusion/ lack of dedicated reading regarding the MR Rib Sided passenger cars.
Since I have Lionel's version of the Rib Sidded cars ( used to have Weavers version with the green film in the windows) I no longer need to feel that I have to have the F7 to feel prototypically correct while running them behind the Atlantic (saved me a fair amount of $$$).
The information of the other manufactures making the Atlantic was also useful.