Here's the site for Modern's Classic Muscle:http://www.oldmusclecars.com/
Ask for Bill. He's always been very helpful.
The ownership of Modern is in the Fowler family. We're lucky here in this part of NC to have two long-established, family owned dealership groups (Flow and Fowler) that are interested in servicing parts for classic GM cars.
BTW, the Chevrolet Customer Assistance Center will send you a listing of suppliers as a part of their past model information. It includes an overview of GM's Licensing Program, a list of Licensees and a state by state list of Specialty Shops/Suppliers, as well as other helpful information and lists for restoration. Those lists are not exhaustive and apparently reflect some sort of direct relationship with GM. For example, there's no mention of Jerry's books or CRG...