It's not terribly expensive to have the Bosch or Bendix units rebuilt. They both use pressurized brake fluid for the power assist, not power steering fluid.

The only practical way to eliminate the ABS system is to find the parts on a similar car in a salvage yard. A Dodge Dynasty uses the same brake system and has the same weight distribution. You'll need the booster, master cylinder, combination valve, and steel lines connecting them. The steel lines going to each of the four wheels will have to be modified to reach the combination valve. If your car has rear disc brakes the master cylinder must be for that application. Master cylinders for cars with rear drum brakes have a residual check valve in that port. That valve will prevent disc brakes from releasing.