Clips too thick... ??....

That has happened before, especially with aftermarket u-joints sourced from other cars, which may have ends 1 mm too long. In a pinch, sand the too-thick clips down on emery paper until they fit comfortably in the grooves provided. Much less work is to obtain thinner clips -possibly used- from a driveline shop or another vendor, some of whom include two thicknesses of clips. Some enterprising owners sand down the two slightly too-long ends on each u-joint. All these methods work if done carefully.
Good that you caught the problem early: a failed halfshaft at speed will do one of two things depending on whether its an inner or an outer u-joint. It will either beat up the pass-through area in the inner fender panel- possibly also taking out the rear brake line (outer joint), or it will hit- and crack- the aluminum ZF case (inner joint). Both have happened multiple times in all years of Panteras.

Thanks Boss... I think I will go ahead and pull them off and take a closer look. I went and bought new caliper today... Thanks !!

Well... It threw another one out ! I have pulled both shafts and I am waiting for four replacement U joints to arrive. I will mark orientation on all components and deliver them to the drive shaft shop and have them inspected and measured for compatibility. If the shop says they will indeed work together, I will have them installed and balanced. You would think that Pantera U joints would actually fit a Pantera??... Frustrating!.. Expensive!.. Dangerous!...

We're dealing with a nearly 40-year-old performance machine thats likely been worked on by inexpert previous owners or clueless local shops. On some cars, the "proper" u-joints no longer press-fit into the halfshafts, and all sorts of problems result. Your driveline shop should notice if the ends are no longer a press fit. There are two fixes but what they will likely do is suggest cutting the (possibly damaged) yoke adapters off and welding new ones on. The other choice is going with a new halfshaft (or two). Finally, you might already have aftermarket Spicer halfshafts in place of the stockers. Unless they've been fiddled with, Spicers were gold-alodined and accept Ford F-500 heavy truck u-joints while stock halfshafts were silver painted and accept stock (larger than Ford) u-joints.

I have learned much about this process in the past few days. The drive line shop has been there 44 years and we feel they will be able to give us proper guidance. The threshold for new ends being welded on is very shallow so I am half expecting to have new, more common and stronger u joints adapted to these shafts. Thank you very much for your help and advice. I will report back....

The shaft shop suggested I lop the ends off and have domestic u joints fitted. The price was very close to a new set of spicers so.... After a kinda' chilled response from the original vendor that sold me the U joints, I started shopping around... Many thanks to Marino at Pantera East ( MAP motorcycle parts ) for setting me up with a nice pair of spicer shafts at a very competitive price. Sixteen bolts later, my car is smooth as can be.... Thanks Marino and Pantera East ...