Thames trucks did not have universal joints at the ends of their axles for steering.
The axle is actually designed from a GMC axle used in military trucks. It was originally built by an Italian Ford dealer who had a number of E27N Majors left in stock. He fitted ex-military axles and called them after his son Manual. Roadless started to convert tractors to that axle here in England eventually building them. The axle design was taken over by Selene.
You may find that military GMC parts fit that axle.
As for axle ratio, as you have an early Super the rear axle crown wheel and pinion ratio should be around 3.3 to 1. The engine is as Robert says, a 2700 Series, possibly a 2703. It would not be the same as a Ford "D" Series truck of the same era as this was an inclined engine to get it under the cab, it could however be one from a "K" Series.
You have Super brakes from the look of it so you need discs not shoes.
They are quite expensive. You also need actuating balls and springs as well as discs if you want to avoid brakes grabbing on. Make sure the adjuster at the bottom rear of the brake housing is free as you need this to set the brakes up.
I would also advise that you look in the rear axle before spending too much. Even with the standard engine, Supers were known for the final drive pinions and bull gears wearing.
