Not sure if this is the sort of info you are looking for or not, but I am aware of at least 3 different FE water pump castings. the real early pumps, (58 & 59) have a much larger thermosat bypass tube (3/4" vs 5/8" for later applications) with the temp sender threaded into the bypass tube. The water pumps used with generators were different than alternator equipped cars. In addition to the threaded boss in the block for the alternator thru bolt, the gen water pumps have a dowel pin, used to position the 1 piece generator bracket. The alternator water pumps replace the dowel pin with a threaded bolt hole, as well as having the bolt boss shorter.
