FWIW the OEM pump I pulled from our '05 was Bosch. But I've been told both Bosch and Delphi may have supplied OEMAbout two years ago we put a Delphi pump in our 97 GMC farm truck. Pump lasted about 1 year and 11,000 miles before going out. Pump had a lifetime warranty so that is what went back in it. Hopefully the new one lasts a lot longer.
And I have no idea who GM may have used on a '97 GMT400