I looked into colors of the impeller and if you get a white impeller from Ford you should be in the clear. It seems from asking around that al the impellers that failed are black in color. The white ones seem to have gone into the 99 and 00's, this is why failures are on the 98 and older mainly.
I ask if the metal pump is a good choice. The pump is underdriven off the cam and it is overdriven itself. So is it really a good idea to use a heavier metal pump? Granted it will not fail like the plastic one but the newer plastic impeller should be fine.
