I am looking for a manual the gives dimensions for different pipe and pipe fittings (PVC, RCP, etc.) I was thinking some manuafacturers might have them, but I don't know any.
You can start with the trade/umbrella organization websites and then find a manufacturer in your area/region. Most of the manufacturer websites have downloadable information/catalogs, or you can get contact information to email or actually talk with a live person.