There used to be a MB parts supplier in Georgia. Owner/employee was Rusty if I recall who owned a 6.3. Gone out of business, bought out, moved, anyone know?
The shop I used and sounds like what you are describing I think was called Atlanta Stuttgardt Auto Parts. They were near me downtown off Howell Mill Rd in the 90s. I quit doing much with my car and they moved North of town to Canton. I don't remember the name of the cool dude I usually dealt with, but Rusty sounds right. Looks like there place turned into a salvage part yard. https://www.usedautopartsdealers.com/state/georgia/atlanta_stuttgart_auto_parts.php