If your Cruiser is weighing in at 7,500lbs to go out on an adventure you bought the wrong vehicle first, and second are bringing waaay too much crap.
To the OP's original question if you are thinking mileage and Land Cruiser, you will be sad no matter what. All gas NA trucks are pretty terrible. That said, the 4.7 hundred will eek out a bit more carrying a load than a 4.5. You pretty much can't go wrong with a 100. They have a great reputation for a reason. They can handle modern traffic speeds and cruise well on freeways not being rolling chicanes like 80's can be. I personally love more old school vehicles and really love 60's, despite their 135hp I have never regretted the 2 I had. They sucked on freeways but for traveling and putting around in the back country they were great. In that context I love 80'sband specifically my FJ80 that I have now owned for 16 years. It is in my eyes the perfect bridge of Land Cruisers of old and new, the last F engine, pretty much a tractor but with modern fuel injection. The coil springs make a great ride and have great flex and the 3FE trucks were the last holdout before the interiors went crazy with luxury. Even with unlocked diffs, my FJ80 could go anywhere my FJC with ATrac and all the aids could go on the same size tires, despite its shorter wheelbase (FJC). Locked the 80's are amazing, but even unlocked they are surprisingly good. IFS vs solid axle to me comes down to slow speed ride in rough terrain. I hate how much side to side rocking you get with IFS as the front end drops into and climbs over holes and rocks. A solid axle levels out the ride more and to me is much less fatiguing when spend many hours behind the wheel. I only mention this because I see it mentioned so rarely but is the most noticeable thing to me. So in rough stuff I still prefer solid axles even if it isn't overly technical. But if you are daily driving the rig, or have to drive freeways much the 100 any day of the week is worth its weight in gold and it can realistically go anywhere an 80 can go when limited to 35's for each. For vehicle based travel though outright capability isn't all as important as payload, durability and to some degree comfort. So yeah a 100 is a better rig in my eyes but lacks character and just feels bland to me. That falls into the whole subjective category of bs I know. Ha! I would rather drive an old 60 that tops out at 70mph than a hundy for a dedicatedly adventure vehicle, that's just me though so take that with a grain of salt. I don't like being removed as much as more engaged with the event. When you go full luxury it's a bit too much removing from the experience in my view.
This also comes from the context of me not being in a hurry when I am traveling this the reason that I don't need a ton of power. I don't get the whole you need a ton of power thing. If you are bringing so much stuff you need 300+hp you need a heavy duty truck likely. You want a 2500lb payload capacity SUV? Get a GMT800 Suburban 2500. I did for towing and it ends up being a great travel rig for getting into the backcountry because no matter how much people or gear you bring, it's going to be really hard to exceed the payload. That's another whole discussion though on how I think Suburbans are the best travel rig platforms for North America. One more point, I used to think I needed every gadget and contingency in my Cruisers for "overlanding" and I eventually realized it completely ruined the vehicle and what I loved most about it. I have since revamped my camping gear and shedded stuff like the roof basket, RTT, etc and still bring what I need but enjoy driving it a lot more again. My last 60 I kept simple too and it was like falling in love all over again.
Dave, regarding the Colorado diesel, we bought one last winter and got it for 10k off the sticker brand new. They are really easy to get for sub 40k. I agree 40k+ is expensive for anything, but we got ours for 32k and 0% for 5 years. We really worked it hard and lucked out but for even say 37k the Colorado Duramax is a ton of truck. I have seen as high as 35mpg on the highway and normally see 30-32. We can tow our 23' camper and sailboat with it too with zero issues yet unloaded it gets better mpg's than our old Outback that we replaced with this. Can't say enough good things about that truck. We looked at Tacoma's too but it was no contest for us.
