Updating a Bradley-type Spring Damped Coupling on Trailer

[TernVI]

Chances are that it's academic, because the old brake assemblies are unlikely to work very well, if at all, after this time.

To get the brakes working in a smooth and safe manner may involve a fair bit of subtlety.
Just slapping bits together and trying it on the public road probably won't end well.

 

[Caraway]

Just get the boat shifted on a flat bed truck or trailer (you are having to hire a tow vehicle anyway).
Flog the trailer as it stands on eBay. Some daft bugger will buy it.