Pinion spline on 489 case

Long shot way to tell the difference is the size of the pinion nut, 1 1/4 is 10 spline, 1 1/8 is 29 spline........although I kinda look at it doesn't really matter what is in there right now as when you buy your new gears, buy a yoke that matches spline count of the pinion you buy, problem solved.