you want the "cancel" mechanism to be symmetric with respect to the straight position of the steering wheel, the return mechanism should be symmetric with respect to the straight-ahead orientation of the steering wheel. My new friend, John York, at York Replicars told me he has to "phase" the u-joints on the d-shaft, but I think it can be done just by arbitrary orientation on the Vega box splines and reorienting the steering wheel.

You probably know this, but the final wheel-straight-ahead alignment is squared away by driving the car then adjusting draglink length to bring the wheel where you want it.

Fwiw - don't set up Pitman arm angle and draglink length so the steering boxes internal stops come into play.
On an early style solid axle front end, that function is taken care of by the stop nuts on the axle.
If stop nuts are new to you - and apparently they are to some considering the cars I see running without them - they're the acorn nuts that hold the kingpin locks in place.

Some of the aftermarket stop nuts - most times stainless and very nice - are overly long and limit the turn radius.
Easily rectified by cutting .120 off at a time and checking the turning radius of the car.
(When my 32 was first up and running it didn't turn very sharp.)
I ended up cutting .250 from the early Deuce Factory stainless stop nuts to get a decent turn without bottoming on the steering box internal stops.
It can be a juggling match to get things set up right, but it can be done.

The stainless stop nuts supplied by the Deuce Factory nowadays is the correct length for most cars.
If memory serves, overall length of the acorn nut is 1 3/16" with a hardened 1/16" thick AN style flat washer.

If you can find a couple of stainless mag wheel lug nuts for Chevy (7/16-NF) there's usually enough room to trim off the shoulder and cut the hex portion down to the correct length thereby saving a few bucks.