Any recommendations for rebuilt steering rack vendors to use or avoid?
Thanks
Tony
SNG Barrett is a really good source.
A1-Cardone I wouldn’t recommend. I’ve had issues with their reman brake parts.
I purchased a rack for my XJS from BuyAutoparts.com It came with great support and warranty I did a quick look at Series II racks and They’re listing the rack, but no availability - it may be a send in yours and they’ll rebuild it. This is common for the older Jag’s because there just isn’t any stock left for rebuilds cause people don’t send their cores back. I don’t send my cores back. I keep them and rebuild them when I don’t have anything better to do. that’s why I’ve got quite the stack of calipers. 
Maval Manufacturing is another company that I’ve sent stuff off to for rebuilding.
You’ll more or less have to send yours in.
SNGBarratt is always a good resource as is Terry’s Jag. and on the west coast XKS.com but I think they got baught out by Welches… Their west coast and have stuff that I can’t find anywhere else. such as the filler cap gaskets for Series I-3 and cheap too.