[LATECH]

You can measure the cap diameter and cross size (width) and check NEAPCO for listing by dimension.You need to check both sets of caps, keeping in mind the cross size may be different for the other set, so be sure to keep track of which part of the joint the caps came off of.
In other words you can come up with a part number by maesuring the joint and picking the one from the catalogs dimensional section, to arrive at a part number, which you can purchase or crossreference for a different brand.
I used the crossreference manual here a while back. Put a 8.8 explorer rear in a 5.9 dakota. Used the dodge drive shaft. Used the hybrid joint and the driveshaft fit perfectly. Didnt even need to cut the driveshaft.

[Rocketbird]

Ok Thanks for the info. During the Fall/Winter months I will take them out and measure them. I think when I take the axle out I will take differential cover off so I can do a good cleaning and refill with some new fresh gear oil.
Maybe that could be a good routine, once every couple of years new differential fluid and new u joints regardless if its needed or not. Or maybe get a plug added to the bottom of the housing or something to make the fluid changing easier. The differential I have only has one plug. . .the fill plug

[AutoGear]

I have a friend with a T bucket; His driveshaft is short...very short and he changes his U-Joints either every 2 or 3 years; just to be safe. His driveshaft angles are pretty bad. It doesnt exhibit any weird behavior though. Well, he had GM Metric front disc brakes on the front and it had a horrendous wobble at 70mph (IIRC). Change to a smaller caliper and the wobble went away.