both SASS & NCOWS sanction both the NMV and OMV ( New & Old Vaqueros ) Stainless & Blue
the NMV only comes in 38/.357 & 45LC I believe ..OMV were/are in 38/.357, 44spcl.
44/40 & 45 LC but are no longer in production.
Only class I know of
you can't use the Vaquero is frontiersman ( C&B class) but then there is the Ruger Old Army C&B.