Try H&H Classic Chevy Parts in Bentonville Arkansas. I think their website is "H&Hclassics.com". They have a full line of parts and the expertise to help you out . They also carry all the aftermarket steering, brake and suspension, and motor mount conversion kits.
Just so you know, sedan deliveries are not trucks. Simply put, they are station wagons with the quarter windows blanked and a single door in the back. Mechanically they are cars.
Panel deliveries, or panel trucks, are trucks. They have 2 rear doors, and are based on truck bodies and chassis.
Hope this helps.