The original Blackhawk, introduced in 1955, was the mid size .357 frame. Then, the .44 Magnum Blackhawk was introduced and it was larger than the .357 Blackhawk. In 1973, Ruger introduced the New Model Blackhawk with the transfer bar. This revolver was/is able to safely chamber six rounds. When the New Model was introduced, Ruger dropped the mid frame .357 and all Blackhawks were built on this larger .44 Magnum frame.
The Vaquero was introduced and built on the larger frame. Many shooters wanted a smaller frame, similar to the Colt SAA, so Ruger brought back the mid frame, with non adjustable sights, and called it the New Vaquero. The first Vaquero, built on the large .44 Magnum frame, was dropped and the New Vaquero became the Vaquero.
I believe the .357 and .45 Colt Blackhawks are built on the mid sized frame and the .30 Carbine, .41 Magnum and the .44 Magnum are built on the large frame.