AJA

Hello All. I'm looking for some advise. I own an S-Type 3.0 SE petrol Jaguar that I have had since 2006. It's on an 03 plate. Its been the best car I have ever had by a country mile. However, it broke down. There is a loud rattling noise coming from the engine like a bearing in a tin can. I took it in for repair and have been told the bearings on the crank shaft have gone and it would need a new reconditioned engine. I ordered an engine from a site called 247 spares and when it arrived it was the wrong one? I'm not a mechanic but was told the cam sensors were on the back instead of the front and it was a different engine. The spare company have been more than helpful but haven't been able to find a replacement. So they have collected the engine and refunded me in full. So here is the problem. I cant seem to get anyone to tell me which engine I need. No one will confirm that what they are offering will fit. There seems to be a few engine codes. How do I find out? Thanks Alan