I just got done replacing the water pump on my XJS and it was a tale worth telling. After 17 years and 103K miles the pump began to leak. I needed one same day so I called the local O'Reilly's and they said if I got a new pump there was a VIN# break in '93 but if I got a rebuilt pump there was only 1 part number for all '93's. They only had the rebuilt anyway so they sent it over and I began installing it. It was a Cardone #57-1407. First problem was the replacement pump did not have the studs for the fan installed and the old ones weren't keen on coming out. O'Reillys had a stud kit to fit several cars with the 8mm thread I needed but when they arrived they were too long and had to be cut down. So the pump finally went on and I am to the point of installing the fan and guess what? The center hub of the pump is larger than the hole in the fan by about .020"! So I had to pull the studs back out and get an angle air tool into the front of the pump to sand down the hub so the fan would go on. I get the fan on and start to put the serpentine alternator belt on the pump and it just doesn't seem to fit correctly. It's like the belt sits on top of the pulley instead of in the pulley. I had to finish the car that day so I didn't worry about the belt for now. The next day I was talking to my Jag supplier about the pump and he said the VIN# break was for either a 4 groove belt (early cars) or a 5 groove for the later ones. So Cardone had the catalog listing wrong for the rebuilt pump. I called O'Reilly and ordered a pump for a '94 and it was the correct 5 groove pump #57-1522. Of course I had to swap the fan studs to the new pump (is including them that expensive??) and on it went. But wait! The damn fan won't go on the hub again! C'mon seriously?? I had to sand down that pump hub as well! So fair warning to you about the Cardone water pumps, I would avoid them at all costs if you can! There is a good chance the same applies to the XJ40 also.