Loosen the nut and turn the long screw and see how much you can tighten it up.

https://www.cmoc.ca/attachment.php?a...ine=1385558298

Centre the steering first ,before attempting this adjustment, there is a high point in the gears. Only adjust the screw in about 1/4 turn at a time or lightly bottom it and back it out about 1/4 turn. Too tight and the steering box will bind on centre.
There is a shop on Trafalger rd (I think that was where it was , I am from London so street name may be wrong. North of the 401 and west of the airport ) They are a uhaul dealer. I came across them last year when I needed a truck.
Mustang specialteaz.? I don,t know anything about their work but there were a couple of early mustangs in the shop.

There is a procedure to re-torque the worm-gear to bearing clearance if you read the Ford manual, however usually when it starts to feel loose the worm-gear is worn and/or the ball-bearings have lost some tolerance.

You can try taking the plate off the top of the box, refilling it with good quality grease, then replacing the cover, loosening the adjuster lock-nut and torquing the box. The adjuster and lock-nut should be clearly visible on the top of the box. Be warned that over-torquing will quickly make your box even worse than it is now, so use the right spec and find the setting procedure in the Ford service manual as there is also a drag spec for how much pressure it takes to turn the steering wheel to the stop blocks.

I have a 1966 Mustang that I did this to a few years ago.