This is a drawing of one type of clip that is used to retain the transmission vacuum line via a 7/16 bolt used for transmission bell housing to engine mounting. It is used on 66 thru 70 289/302 and 351W/C with C4 and FMX automatic transmissions. It is identified as "7B085" which is the complete reference on chassis drawings. The 75 MPC say to fabricate a replacement. As it does not have a valid Ford part number, I have assigned UNK52. It will appear as such in the next version of the Mustang Hardware Spreadsheets. The drawing is intended to identify the clip, and if you really get ambitious, make one.
Jim