Another Driveshaft Question

[Chatt69chgr]

My drivetrain will be 440/4-speed/8-3/4 in 69 Charger.  Previous querys from everyone indicated that the driveshaft length would be 52-1/4 inches centerline to centerline on the u-joints.  I went to look at a pile of driveshafts today and never did find one this length.  Closest was 52-1/8 inches.  I figured that would work.  I didn't pick it up since it had something on it I had not seen before.  On the transmission end of the drive shaft there is a large round piece of metal maybe 3/4 of an inch thick welded to the driveshaft tube.  It is located maybe an inch or so back from the u-joint yoke on the driveshaft and completely encircles the driveshaft tube.  Is that what was supplied on Chargers?  What is this for?  None of the other driveshafts I have seen in the junkyard had this.  Now they were not on Chargers but on Coronets and other 69 B-bodys with 318's as well as C-bodys.  A picture of the correct driveshaft and corroboration of the 52-1/4 inch length would really be appreciated before I fork over any money.

[Chatt69chgr]

No replys needed now.  I determined that the correct length is 52.07 inches and the metal ring on front of driveshaft is a vibration dampener.