When we were building the drivetrain for the car the driveline was way off lengthwise as we went from a 904 transmission to a built 727 and the rearend was a 7.25 so when my son had the driveline made for the car he initially was going to use the big pinion 489 with the 3.23 sure grip. So he had the driveline built with a big pinion yoke. I’m sure we can just use a conversion u joint to make it work with the small pinion. I think he was just hoping to use the 489 case. Thanks for the information.