Which 3rd member is correct for my car?

Hello guys I'm needing some help with my rearend. I have a 1967 fastback formula S 383 auto. My 3rd member is bad and I need to replace it. It has a 489 housing which I know is wrong. My question is which housing and size yoke am I supposed to have? My driveshaft is the small yoke. Has it been changed? Did automatics use the samll yoke? 741 or 742 housing?
Adam
440-258-3009

In most cases you would find a 741 case with a 3:23 SG unit as standard equiptment, with the 3:91 being the other option most chosen. However, because your car is a big block car, it is possible that your car could have had a 742 case. I will check with my buddy to see whats in his car, his is an all original 68 383S convertible. It's a 4 speed though, so it is not the tell all, and maybe there are others here with more info. Geof

yet the 489 case is way stronger then the 741 although the 742 case might have been in that vehicle. Whichever gear ratio you choose to run keep the 489 case as a spare.