I found good information in the 1968 Chrysler parts catalog.
The type of pump in 1968 was determined by the design of the shaft's end and the inside diameter of the reservoir.
The end of my pump's shaft is smooth and the inside diameter of the reservoir is 4-5/8".
That makes it a .96" displacement pump.
And by the way, a 1.2" displacement pump would have a "hex" shaped hole in the end of the shaft and a 5-1/8" inside diameter reservoir.
Two other pumps were also offered:
.94" displacement (Key slotted oil pump shaft w/nut, Saginaw-built, 273 and 318 cid engines)
1.06" displacement (3/8" threaded hole in the shaft, 4-7/8" I.D. reservoir)