I recently picked up a 53 1/2 ton with a 235. The casting number shows a 54-57 block. The generator pulley didn't line up with the harmonic balancer and the water pump so I put a spacer in line to even things up. I just burnt out the generator and need to know how to replace it with the right one. Do I need the long or short shaft one. I've converted to a 12 volt system. Any ideas?