Tires - 37 or 40?
 

I'll start out by saying I'm in Phoenix and wheel all over Arizona. Up until this point I've been wheeling on 35s (which short arms & 6" lift) it's been quite rare that this setup hasn't been big enough. However, I'm about to swap in a V8 so the XJ D30/D44 combo is going away. I'm going to be swapping in 1 tons (05+ Ford SD axles) and this weekend I started laying out of a 3 link (2 lowers, 1 upper, track bar and drag link) long arm setup. I may have to push the steering box forward a few inches to keep the drag link angle correct, but I'm okay with that/well within my abilities. I'm not interested in going to full hydro as I drive this to/from the trail.

In the picture (a few weeks old), you can see the (then planned) cut mark on the front fender. With the axle pushed forward 3" and centered in the cut, I have a 36 inch "gap" between front and rear corners. I haven't bothered with the rear yet, but I can do whatever is necessary back there.
https://cimg6.ibsrv.net/gimg/www.che...af9d8f1f14.jpg

I'm trying to figure out if I go 37" or 40" on tires. My gut keeps telling me 37 (or 38), but I could use some extra input to make sure I'm not missing something. It's not a comp vehicle, it's a "go anywhere" vehicle. It gets loaded up with me/wife/kids/dog/etc. and we go play (a few hours/a day/camping/etc.). The goal isn't to climb a vertical wall, it's to ensure that no matter where we go, we can get through AND get home.

I am thinking of going to 40s too. After measuring, I think that you will have to move the axle 3" forward to do it. There is also the issue of axle width, which you should have covered so you can turn the wheels lock to lock
What are you going to do for the rear fender well. I have a two door, so I don't have that issue. But 40s are a lot of tire for that fender well unless you are going to move the rear axle back and move the gas tank

Any other input (ideally from someone who has had both)? Is there really a significant advantage for 40s over 37s?