I'd certainly try Legendary. I think Classic Industries may resell a lot of Legendary's products, whereas Legendary is a manufacturer.
Legendary lists Pearl White Boar Grain for C-Bodies. Maybe they can get a piece large enough for your 'Cuda.
69 NEWPORT/300/NEW YORKER VINYL TOP - PEARL WHITE BOAR - Legendary Auto Interiors
They also have an address for your questions:
[email protected]