The "Old Model" Blackhawk/Super Blackhawk models were sometimes also called "3-Screw" models, indentifyable by the 3 screws through the sides, instead of the pins.
These "Old Models" did NOT have the transfer bar system, so unless later modified by Ruger to the transfer bar, SHOULD ONLY BE CARRIED 5-UP, that is only 5 chambers loaded, with the hammer resting on the empty cylinder. The new models can safely be carried with all 6 chambers loaded.
The latest "New" Vaquero has the slightly smaller grip/frame, more like the original Colt SAA revolvers, but still has the transfer bar. Vaqueros are fixed-sight guns, while the Blackhawk series guns feature adjustable sights.
Some of the Ruger Gurus should be along shortly with anything I missed.
If you send in your "3-Screw Old Model" in to Ruger for any service, and it hasn't been previously 'transfer bar modified', it will be.
I had one of the very last of the 3-screw models .357Mag Blackhawks years back, and I think it had a slighty smoother trigger than the new ones, due to the transfer bar system.