My 69 P@A shows that the plastic injected 1330 series u-joint was only used in 67-68 w/T 400 and the driveshaft pinion flange used straps.
The 69 used 1300 series u-joints with straps. The 67-68 used 1300 series but used u-bolts.
I have no idea why GM used the heavier 1330 series u-joints in the 67-68 TH 400 and not in the 4spd.
The 69 P@A also shows that sometime in 68 there was a second TH 400 designed driveshaft with lock rings. I may dispute this as I ordered my 68 in late July and received it in Aug.
I am trying to get the build date of my 68 but that is another very sad story.
If anyone has different or additional info. on this subject , chime in.