The best time possible at Tonawanda = 30 minutes on the pouring loop to shake out on lines 1 & 2 (block lines) + 4 hours in the cooling court + 20 minutes through blast, grind, chip & inspect. The door to the Tonawanda Motor Plant was only about a 50 foot fork truck ride from the end of both block finishing lines. Sometimes the blocks were pretty warm when they arrived at the motor plant. At that point, the block could go right to the motor plant machining line. So...it's clearly possible for a casting to be produced and assembled the same day. We weren't "just in time" in those days though. Most casting waited on pallets in inventory que. If a block fell off of the conveyor in the cooling court it would sit up there until Christmas or Summer shut down. So a casting date could be many months before build date. The Flint motors would be pretty difficult to be cast & machined the same day due to the trucking required between Saginaw & Flint.
I didn't realize there was a Christmas shutdown. Was it more than just that day and Christmas Eve? What about the New Year's holiday?