The 295/50x15's will give you a noticeable RPM drop @ 100kph. Doesn't seem like much but with 4.11's @ 3200rpm an extra 200rpm needed at 100kph with 265's feels like heaps! Around town 4.11's are fine. They suck on the freeway with toyota hatchbacks passing you. You'll generally cruise at 3000rpm doing about 90.
Even with the 4.11's @ 7000rpm (295/50's) you'll be doing 134mph. At 6500 you'll be doing 125mph. EITHER one of those is a huge MPH for crossing the finish line at the strip.....reflective of a 10 sec car. SO..........with a higher diff ratio, you will definitely be passing the line well below your peak RPM and not optimising your set up.
Personally I say go the 4.11's!! sounds like you'll be doing a bit of racing and I reckon you'll only kick yourself with anything higher. Get that big heavy XA hauling some mail!
Here's a driveline link you can play with. (transfer case ratio = 1, 4x4 thing!).
PS: let us know when you'll be running it!