I would go to one/a few SASS events and check it out. You will see for yourself what is used and the SASS members will be glad to tell you everything you need to know.
Generally, an 1873 rifle with short stroke kit .357 shooting .38 Special
A pair of Ruger Vaqueros .357 shooting .38 Special
A Shotgun - number of options
The guns sold by Evil Roy work - he would know