The data for my 1992 SC300 shows the differential to be 4.273:1, the O/D .705:1, making the final drive ratio 3.012:1
With my 26.6" (275-35/19) rear tires, that's 26.3 mph per 1,000 rpm.
60 mph = 2,286 rpm.
70 mph = 2,667.
Mine has an "OD" + "D" lamps on the dash