Yes, my 84 & 85 300D's do have IRS, so maybe that is where they take care of axial motion. Makes since because there is a center bearing that locks axial position before the front rubber disk. Those rubber disks fail and sometimes turn the driveshaft into a pole-vault stick, or a cutter than slices right thru the transmission tunnel. With our U-joints, either ball & trunnion or standard, all the pieces usually stay together, at least from the normal needle bearing failure mode.