I'd be glad to assist, but I have no idea what you mean by a "period correct" chassis.
Can you be more precise about what information you are seeking?
Also, are you sure your VIN's last four digits are 8735? Or perhaps that is the engine block #?
Your VIN should read THPNXX0XXXX.
Chassis #'s in the 8000 range are basically thought to be nonexistent. See this from the Pantera History section on the Home Page:
DeTomaso made a jump in chassis numbering between the last Vignale coach, 7554 (?), and the first Maggiora coach, 9001. Bill Van Ess, an esteemed historian of the DeTomaso marque, claims the Pantera with chassis 9001 was assembled on June 13, 1976. One odd-ball Pantera has a chassis number that falls within the gap in the chassis numbers, a group 3 Pantera with chassis 8472.