Your engine is on it's way out and your trying to do some research on replacement options. Replacing or rebuilding your air-cooled or Waterboxer engine can be expensive but an alternative to the VW engine, is to swap it for a powerful, reliable, Subaru engine. For most Classic Volkswagens you can swap the engine yourself by reviewing the following lists, following the Youtube videos, or for a Vanagon, follow the SubaruVanagon articles and dive in.
For even more info, check out the RESOURCES page.
Email firstname.lastname@example.org for more information regarding your VW Subaru swap project.