These guys seem pretty good, FCP Euro? They seem more customer responsive than Autohaus and offer lifetime parts replacement and free shipping if you wait 7 days to get it etc.? Trustworthy? They immediately send you a copy of your chat too. I have good experiences with Rockauto also, but they seem a bit more low end and not always the right part. Does anyone have any other recommendations.

In case anyone is interested I am getting a DENSO Alternator for a 2013 XJ 3.0l V6 SS from FCP Euro for $254.99 plus inexpensive rush shipping. Does that look like the right part ? They checked my VIN and said it was..., but you never know and the intelligence on here is a cut above !!
https://www.fcpeuro.com/products/lan...enso-lr023421g

At Harper Jaguar where some prices are very good (especially the latest version of the water pump at 232 vs 330 at FCP) that Alternator appears to be $900... - Jaguar (C2D59622)
https://www.fcpeuro.com/products/jag...aguar-aj813909

 

Most of these are brand labeled and this practice is not unique to Jaguar. FCP is nice because they offer a lifetime warranty if it fails. If the part fits in their configurator, I haven't had an issue.
I'm not sure you'll have anyone taking the time to triple check your part. The dealer will confirm it for free (at least the OEM PN).