anybody running this differential

I cant do anything right now till I get the old rear out and figure out which spline yoke I have in the old one unless I get another one if it is wrong. I had planned on going with Richmond gear and it is a 10 spline. may have to go with a 29 spline. anybody have a guess which spline was used in a 489 case with a 2.94 open. probably would just be a guess wouldn't it. stopped in my tracks.