3.08 to 3.42 posi- questions

[vtwinsport]

Hey all,
Just dropped my 12 bolt 3.08 open differential. Put in a 3.42 posi from an 87 suburban. Drums and shoes fit, leafs and shocks fit, the u joint on the pinion basket (yoke) is larger than the u joint from the drive shaft side.

The 3.08 uses a 1 1/8th u joint cup. The 3.42 uses a larger and wider one. Anyone know what that is?
Also, can I just change the u joint on the drive shaft rather than change the basket on the pinion shaft? Or, do I need to change the drive shaft? The pinion shaft on both differentials is 27/32 and the 3.08 takes a 29mm socket while the 3.42 takes a 32 mm socket (or imperial equivalent) so the baskets should interchange. *** Edit- Found out that the yokes can't be swapped- has to do with tolerances.***
See picture below of 3.08 basket (yoke). and 3.42 under the truck.