Don't waste time trying to repair the hydraulic brakes. The front slave cylinder was deemed obsolete and at this point, illegal to hook up to any motor vehicle that has a dual brake system, which took place some 25 years ago.
You can replace the brakes with 12 volt
electric brakes. However, you might have to have the outer edge of the hub and drum assembly cut down so that the drum does not hit the backing plates.
The brakes you need are 12 inch.
Or, shortly, a disc brake system will be available, which is far superior to any electric brake system ever designed.
The wheels must be a minimum of 2600 pound rating, and the bolt pattern is 6 on 5 1/2. We have them if you can't find them locally.