questions and/or statements which may relate to finding out if this is original.

the '69 axle tubes were flattened on top for a few inches along the tube. the 67-68's were not. were there any other cars which had these flat spots? does the rearend in question have these?

some of the early cars (possibly only '67) also had eylets welded to the tubes for the swingarms on coilspring cars.

the KH on the drum i do not see in the online manual, but i also don't see an SP code for a 350 with a turbo tranny, so the manual, although indispensible, is fallable. (i have also found other part #s in that manual which are different, or dont seem to exist) and apparently you could order these cars just about any way you wanted them.

anyway, i do see an XH for a 3.55 gear. maybe the part of the X is worn on the drum stamping?