The New Vaquero and other "mid frames" take the same hammers as "New Model" large-frames.
I dropped an SBH hammer into my New Vaquero and it needed no tuning whatsoever. I really like that hammer, better than the "Montado" variant. The Montado hammer is the same thing as the SBH except for the checkering pattern on the thumbpad - Montado (and the new "SASS special") hammers are diamond checkered with a border, SBH has horizontal unbroken lines running side to side that make slipping your thumb off at the end of the cocking stroke a joy. Ruger got that one RIGHT.
If installing a Bisley hammer, the good news is that the area you have to modify at the back isn't at all a "critical tolerance" situation. As long as all the holes are there and it looks halfway decent you're good to go. The OTHER side is where the critical sear surfaces and the like are and you shouldn't need to touch that unless the "push-off test" fails, in which case yell for help here
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