The original Blackhawk was made on a Colt SAA size frame (roughly). These were all "Flattops".
When Ruger brought out the .44 Magnum ('56), they still used that frame size, but lengthened the cylinder window a bit for the long .44 Mag round.
In 59 Ruger began producing the Super Blackhawk, on an all new frame of larger size, with the hump on the topstrap protecting the rear sight base. Same frame they are still using today.
Ruger built both the .44 Blackhawk and the Super Blackhawk until about 64 when the original flattop frame was dropped. And some time after that, began making the Blackhawk on the large (super blackhawk) frame. These are the "3 screw" Blackhawks, not flattops and are all on the large frame.
In 73 Ruger introduced the "New Model" guns both Blackhawk and Super Blackhawk, all on the same large frame with the transfer bar system.
When Ruger wanted a gun to fit the Cowboy action rules (fixed sights) they used that same large frame as the Blackhawk, just recontoured the topstrap to a fixed sight gun, and named it the Vaquero.
Ruger eventually dropped the Vaquero, replacing it wth a Colt size gun, named the "New Vaquero".
And, now, Ruger is also offering a recreation of their original Flattop models, but with the "new model" lockwork. These are Colt size guns.
So, there are 5 different "Blackhawks" possible, the original Blackhawk, the original Blackhawk in .44 Magnum, the large frame Blackhawk with the original Colt type lockwork, (3 screw) the new model Blackhawk (large frame, transfer bar) and the new Flattop model with the transfer bar lockwork.
As far as I know, none of the original Flattops was ever made in .45 Colt. Some of the large frame Blackhawks with the colt type lockwork were (approx 70-73) and after 73 all .45 Colts were large frame new model Blackhawks.
Until recently when Ruger brought back the smaller Flattop frame size Blackhawk and chambered it in .45 Colt.
clear as mud now?