Jeffrey Ross writes:

I'll add my $0.02 as well... last April when my Aztec came due for its
annual ('69 D model) I considered the price of the tube and the labor
involved in pulling to tube to inspect it, and redoing the inspection
ever 500 hrs I decided to be done with it an just replace the tube.
[...]

Likewise.

In other words remember that these planes were really built one at a
time and the instructions are just a guide but not always definitive.
[...]

The mechanics doing this work on my birdie decided to remove the old
torque tube and send it along with its blank replacement to a CNC
machine shop, in order to exactly duplicate the old one's drilling
pattern.

- FChE