Look at the input shaft of the gearbox as you easily turn the steering wheel off-center r and l. IF that gear input shaft moves in and out, THAT can be where the play you are feeling really is, NOT with the normal adjustment on the top of the box. There is an adjustment for that, but it takes a special spanner wrench to do.
Otherwise, check the coupler at the base of the steering column. It can be another place for age-related slack. Allegedly, if the inside is clocked 180 degrees off, it can cause slack, but if clocked correctly, no slack. I heard an alignment guy mention that one time. FWIW
Presuming all of the varioius steering linkage-related items are tight and in-spec?
Do ALL of the off-center slack tests with the engine running, too!
Seems like the Borgeson steering box is actually for a late-model Jeep application, with necessary adapters to fit things other than Jeeps?
Enjoy!
CBODY67