Ford extended the production of its 2004 model F-53 chassis with a 310hp V10 and "Ovedrive" button on the shift lever (4 speed) till December 31st of 2004. On January 1, 2005 they began production of the 2006 F53 with the newer 362hp V10 and the "Tow-Haul" button on the shift lever (5 speed). It was a huge upgrade for the chassis. The 2006 chassis is much preferred but the older F53 isn't bad either. It's just that the extra gear and horsepower really make a difference I'm told.
The 10th digit of the VIN would indicate the year of the chassis.
You can decode the VIN at this webpage:
https://www.vindecoderz.com/EN/Ford/F-53