As an addendum to the above, via the Pictures From The Shed Program:
The item at top of pic is the 164's relay bracket and idler arm (big bracket) while below it is a 140 relay arm bracket fitted with a 164 idler arm.
The 164's relay bracket and idler arm is listed as a single assembly (p/n 678928-3 for RHD - Group 6, page 2, item [10] of the 164 parts book) and likewise the 140's is also listed that way (p/n 1212484-8 for RHD - Group, 6, page 4, item [10] of the 140 73+ parts book),
However, both 164 and 140 share the same bush - p/n 671444-8 - which allows you to put the 164's idler arm on the 140's bracket when you're putting a 164 power steering box into a 140.
So if you're planning to do a 140 power steering conversion from a scrapped 164, make sure you also salvage the relay lever and bracket as well as the power steering kit.
The Pittman arm from the 140's steering box won't fit on the 164's power steering box, which is why you need to do this change.
Here's a better view of the bush on the bracket (and youbetcha - this bush will be changed before seeing service again!)