Sorry I doubt it.
Having worked in manufacturing operations my entire career I have a good idea how it works. Stamping the carb body was likely one of the first steps in manufacturing. They then had to be built, tested, and packaged. They had to be moved to shipping where they remained in queue until loaded on a carrier. Holley was likely under contract to supply carbs at a certain rate to each plant. Chevy averaged about 65 Z/28s per day between the two plants with 80% of those at Norwood. The second worst thing a Tier 1 can do is shut a line down with a part shortage so the supply chain is designed to virtually eliminate that possibility. Expecting parts built 2,200 miles away to arrive a few days later would require premium air freight and expedited handling at considerable additional expense. Carbs were probably shipped in weekly batches by rail to Van Nuys, maybe trucked to Norwood 260 miles away. Shipments wait be be unloaded, have to be checked in, must be moved and located. All takes time; all predictable. Suppliers cover their butt with stocking warehouses and safety stock.
So no, I do not believe a carb built in Detroit on Monday was on the assembly line in Van Nuys a few days later.
