Twenty years ago my slip yoke went oval and roached the output bushing in my super-T10. The shop that did the repair work tossed what was probably an original-ish yoke and did an upgrade to something they claimed was heavier duty. I remember them telling me they had to do a u-joint conversion. Today is probably the first time I ever really looked this all over. Sure enough there is a special u-joint in there. Half of it is those inside C-clips (standard GM stuff I guess since it looks like the joint at the pinion); the other half is spring clips on the outside. Which conversion u-joint is likely? Is this a 1344 to 1330? Thanks
Bust out yer calipers. Once you have the ends of the cross identified, as to type and size, you can find several combo u-joints that should be correct. http://www.driveshaftspecialist.com/HTML Measure/UJ ID Guide.html
Yep, you'll need full width of it both ways, plus cap diameter and style and which goes where. Our Oreilly's usually has what I need in stock, I just take the old one out and bring it with me to cover my a$$.
Since it is a Buick,my educated guess would be a 3R joint for the driveshaft,and a 1350 for the yoke.