Well, I have a Thames assembled corona. (2.0 GL model) These seem to be a very budget car for a few reasons, 13's instead of almost every other corona's 14's, 3s-f (carby)... there is no mention of that engine on any of the catalog sites, also a four stud wheel pattern.
My question is: Which toyota's with a four stud pattern have rear discs?
From around 1990 onwards.
you might find AE82/92/101 Corollas (esp FX-GT), Levins/Truenos etc will bolt on, as it seems that the majority of Toyota brakes swap around quite easily.
You could even run a combination of calipers/brackets from a Celica and disks from one of the above mentioned cars.