I wasted half my morning trying to figure this out. Best I can tell you are correct - you need to get
DAN1103, and forget all the stupid LR part numbers. It appears the box you received has wrong labels attached.
Here's what I had learned over the past couple of hours:
I double-checked a dealer site (LR Tampa). That is showing three total supercessions, four total part numbers, for LR4 5.0L V8 as of chassis AA538493: LR023421 --> LR065246 --> LR091107 --> LR124471. Also, Jaguar C2D42135 should be identical.
And, from photos, everything points to
DAN1103 being correct, and DAN986 being wrong.
I can't figure out why the Denso box has LR091107, LR124471, and LR023421 on the upper/left label (should be correct), plus LR023421 (also correct), with DAN986 (not correct).
Britpart has some photos of an alternator which looks like DAN986 (shows different p/n, YLE500410) which is for LR3/LR4 with 4.0L V6 engines. AutohausAZ shows YLE500410 crossing to DAN986.
https://www.autohausaz.com/pn/DE-YLE500410
All of which is a long-winded way to confirm you received an older 6-cyl alternator instead of the V8, and the box labels don't match. Aye caramba. Microcat seems to confirm LR008862 and YLE500410 (DAN986) are for the 4.0L V6 engine, not offered in USA, AFAIK. The dealer supercessions don't make sense though.
Dealer supercession chain starting with 4.0L V6 alternator:
LR011231 = 4.0L V6 / to chassis AA538493, 2010 V8 Range Rover?
LR023405 = no fitment shown
LR065865 = no fitment shown
LR077418 = no fitment shown
LR091107 = LR4 V8, and 2011-2012 V8 Range Rover?
LR124471 = LR4 V8, and 2011-2012 V8 Range Rover?
Dealer supercession chain starting with 5.0L V8 alternator:
LR023421 = 5.0L V8 / from chassis AA538493
LR065246 = 5.0L V8 / from chassis AA538493
LR091107 = 5.0L V8 / from chassis AA538493
LR124471 = 5.0L V8 / from chassis AA538493
Note the 4.0L V6 supercession chain switches to V8 alternators at the end. This seems to be the source of the error, but I can't tell for sure. Worse yet, other dealers (i.e., Land Rover Cary) show
different supercession/fitment info, at which point I gave up.
Microcat screenshots below; note the DAN986 equivalents are "up to chassis AA538493".
I had a really hard time locating photos of a Denso DAN1103 box+label that also showed the alternator coming out of the box. I did find a video of LR091107 / DAN1103 which appears to visually match the original alternator you removed from your truck:
