Although the casting number is the same and was used in both model years,I don't think it will work properly on a 67 do to an ommision of an internal check valve.
Both the 67's & 68's used either a Manual drum or Power drum M/C both stamped
BS,or a Power Disc. M/C stamped
WT.
But the
AD M/C is a Manual Disc. application exclusive to 67's.