Maybe yes. I'm guesing by "Vaquero" you're referring to the Vaquero and not the New Vaquero (Too many folks don't get the differetation and confuse them) Theoretically the cylindr will fit and function but the importnat thing is that it's timing is correct. Many will simly drop in but it's best to double check the alignment and timing BEFORE shooting it.
There actaully was .45 Colt/ 45 ACP Vaqueros made in small numbers as a distributor model I believe for Davidson's.