I love my LR3, but there is no way in hell that I'd wheel it like the Jeep. Unfortunately, the FJ60 I had was more of a Family Truckster than a 4 wheeler. When I did hit the boonies with it, it was always a very capable off road rig. I have seen some built 60's that I just drooled over - lifted, wheels and tires, all the expedition racks, etc. And the 6cyl. can be built into a real sweetheart of an engine.
I know you mentioned diesel, but the 6cyl. in the 40's and 60's is an incredible engine. It's essentially a direct copy of the old Chevy Bluestreak and many parts are interchangeable. I always ran Chevy mechanical advance distributors in mine. When I blew the six banger in my FJ40, I went the popular route and swapped in a V8 and auto. While having a 327 cranking out 290 hp and mated to a TH400 with a tow truck shift kit was fun, I missed the 6cyl. and 4 speed when wheeling.
I still think you should take a serious look at an FJ60.