All pretty easy. The interference fit between the (soft) iron pulley and hardened shaft, keeps corrosion between the two minimal. Once it starts to move, it comes right off.
The impeller isn't too much of a problem either. The easy way is to remove the grub screw locking the bearing housing to the pump housing. You may have to drill it out and tap using a helicoil or thread insert. The grub screws are 8 mm and easily made up on a lathe. Then the impeller, water seal and bearing housing and shaft are pushed out of the pump housing with a hydraulic press. Then a fixture is placed under the impeller, (I use a steel pipe), and the shaft is pressed out of the impeller.
At this point you may notice the corrosion of the pump body both under the impeller and BELOW the waterseal in the recess. Time for media blasting. That done, the pump body corrosion can be repaired on the big water tube, with JB Weld, then ground and sanded down to match the original profile. I paint the interior of the pump and tubes with black epoxy paint. DO NOT paint the water seal area or bearing bore. You can also paint the impeller after media blasting. Then the water seal body bore (and pits) are coated with Permetex-Ultra-Grey, just where the seal presses into the body. The new seal is installed with a correctly sized socket and LIGHT hydraulic press work, or a dead blow hammer. Next the exterior of the bearing holder is lubricated, and installed being sure to line up the grub screw hole with the hole in the body. Install the grub screw.
Now examine the seal rubbing surface on the bottom of the impeller, and lathe cut and polish as smooth as possible. lubricate the shaft, and press the pump body with bearing and shaft onto the impeller until the shaft is flush with the outside flat face of the impeller. This should compress the water seal spring, causing the seal to ride firmly yet smoothly on the seal surface of the impeller.
Next, paint your pulley, lubricate the other end of the bearing shaft, and press the pulley onto the shaft, again, so the shaft ends up flush with the front face of the pulley.
Completed, the pump should turn freely with only friction from the water seal.
Here are some pictures Dennis, of customers jobs in progress and completed.
Worst case, you can send the whole thing to me to rebuild, OR for LESS MONEY, buy a good after market pump. Most of my water pump builds are either for show cars where the original body casting counts, racing, where the owner wants to be sure or change pulley sizes, or conversions where 750 or early 101 pumps want to run plastic fans, narrow pulleys and more modern internals.
The first four pictures here are epoxy repair of serious pitting. The next post shows odd completed pumps.