The Classifications start on page 7 of the January 2005 - Eleventh Edition of the SASS Shooters Handbook.
CLASSIC COWBOY/COWGIRL
• Handguns: Any SASS legal Traditional Category pistols shot Duelist Style
• Calibers: .40 caliber rimmed cartridges or larger - pistols and rifle (e.g., .38-40, .44 Special, .44 Russian, .44 Mag, .44-40, .45 Schofield, .45 Colt) or .36 caliber cap & ball or larger.
• Ammo: SASS legal ammo - smokeless or blackpowder
• Rifles: Any 1873 or earlier manufacture SASS legal rifle or a replica there of (e.g., 1866 Winchester, 1860 Henry, 1873 Winchester)
• Shotguns: SASS legal external-hammer double barrel or lever actions
• Costuming: Must choose at least five of the requirements listed below. All clothing items must be worn appropriately during all shooting events and awards ceremonies. Chaps, spurs, cuffs, tie or scarf worn loosely around the neck or with scarf slide, vest, pocket watch with full-length chain, jacket, sleeve garters, knife, botas, leggings, braces; no straw hats allowed.
FRONTIERSMAN
Same as Frontier Cartridge except handguns are limited to .36 caliber or larger percussion pistols shot Duelist style.
There isn't an official Senior Classic Frontier class, but a local club could have one.
The stage instructions should explain what the sweep is, if not, it is a poorly written stage. For example, the Nevada Sweep on three targets is T1-T2-T3-T2-T1.
I don't know if there is an official list of CAS terms anywhere.
Hope this helps.
Slim