I can't help you on the interchangeability of grip frames between the Vaquero and New Vaquero. I know that the latter's grip frame is smaller, though.
Ruger makes a Bisley version of the New Vaquero; there is only one finish (stainless) and barrel length (5.5 inch) available but you can get them in .357 or .45 Colt. Here's the link on Ruger's website:
http://www.ruger.com/products/vaqueroBisley/models.html