Just finished rebuilding the entire suspension on my 2006 XJ. When I was looking for parts there seemed to be some confusion on the rear lower control arms for the 06+, being that they are different from the earlier cars at the knuckle end. After some research I'm happy to say the Delphi lower arms from RockAuto (TC3774/TC3773) fit perfectly and saved me a bunch of $. One side was around $120 and the other side around $130. Way less than OE parts and quality seems good (can't be any worse than the crap bushings they put on the cars originally).

Ended up doing the rear upper/lower arms, rear toe links/sway bar links, front upper & lower arms, tie rods/sway bar links, and new front air springs. Car only has 60k miles and rode fine, but what a difference. Haven't driven it much since it needs an alignment. Going in for that tomorrow and then I can put some miles on it. Used Delphi from RockAuto for all of the arms (rear lower, front lowers, front uppers) except for the rear upper (Moog), and used Moog tie rods front & rear. I think it was around $1k total for everything, nowhere close to the cost of OE parts and everything fit well and looks/feels like decent enough quality. Happy to share any other part numbers, but everything else seems to be pretty well documented except for those 06+ rear lowers. Hope this helps someone.

Well The Lemförder Oe (all arms and steering)
parts all round were about the same price than what you put on

No chance Lemforder parts were anywhere near the price of the Delphi/Moog. Just the rear lowers are $300 each...

175€ past G41511
230 € before G41511 early x350 in Europe

Can't get them that cheap here, wish you could. That's still $205USD per side, $150 more than I paid. My post was more to help people in the US that don't have access to the reasonably prices Lemforder/OE parts you guys do over there. The rear lower arms in the US are well over $300USD each here in the US. When I was trying to find PNs for this stuff a while back there was a lot of confusion on the 06+ arms which are different than the 03-05 so figured I'd post in case it helped anyone in the future.

Car is at the alignment shop now, should be able to pick it up later today. Hoping it rides like new again after replacing everything. Not that it rode poorly even with the disintegrated OE bushings, but hoping for some improvement and definitely will have peace of mind now that its done.

For rear lower suspension arms by LEMFöRder OE would be:
Early x350 2003 till 2004 or 05
Vin G00402 till G 41511 included( smaller bushing)
Left side 39839-01
Right sde 39840-01

then: from Vin G41512 on and the starting with H
X350 x356 and x358 till 2009
Left side 39713-01
Right side 39714-01

What’s the difference between the early version and the later version? Are they interchangeable?

You can use the earlier(more expensive)model ones on younger cars but then with shimms cause the width diffrrence of 1 or more bushing/s .
the other way around they will not fit.

How about the rear upper arms? Do they also have a difference between early and late X350? These are much cheaper when they’re sold for the Lincoln LS but I’m not sure if they’re compatible - they do LOOK similar from the pictures online. Thanks again

Rear uppers are the same from 04-09 and are shared with the Lincoln LS. I used Moog rear uppers for a Lincoln on mine and they fit just fine.