Casting number on the 1.5 ton diff head is 36522??, maybe 3652280.
The casting is 350mm/13 3/4" diameter at the mounting face. 1115 mm/43 7/8 inches circumference, and is retained by 10 bolts.
The rear cover is 340mm/13 1/3 " diameter, also retained by 10 bolts.
