I have always had great results using a new Carter 6588 mechanical pump when replacing an old worn out one. Never had any issues with them and they last for many years, trouble free. I'm not sure they can be rebuilt but, a new one is only about $30.00 or so. This is for the V8 engine, the number for the inline 6 is 6399. The last time I bought one at CARQUEST I had to wait a day for them to get one from the warehouse.
Mark.