The truck is a 6.0. And the only reason I'm even thinking of getting rid of it is due to expensive and extensive repairs. I've bulletproofed it, but now it's just little things here and there going wrong and needing fixed.
I've spent roughly $5k in the past year alone. Now it's been a very strong truck, and very reliable other than the time spent in the shop getting it's heads studded, and egr deleted.
A friend schooled me on that Ford 6.0 and it sounds like you've done most of what needs to be done to make it more reliable overall. To me it's like you might as well get the good years after having done all that.
Now, if you are so used to having "little things" go off frequently, then sure, get a high mileage LR3

I think you're truck is more solid though than mine. An LR4 as mentioned above would be nice but that's like 2x the $ and still no guarantee it won't cost you just as much over 200k for repairs and maintenance.
You can totally bring a dual sport with you though on the truck. I like this idea because it opens up trips like haul to the Rockies, then day trip from base camp on the bike. The drive is easier on you across the country, then the rides are more fun because you aren't having to haul everything and break camp and set up again each day. You'd have the option to do a multi day loop though too though.
I also like the potential your truck has for a small to enormous camper that can be left behind at camp sites during the day which allows the family to come along, etc. Bringing a bike allows the family to come but also for you to explore trails where a full size wouldn't go so easily or even a Land Rover. Many options with the truck plan.
This is all of course coming from my own ideas but also what it sounds like you might enjoy too. Long term, maybe you simply wait to afford the Land Rover when it can be added rather than replace the Ford.
Honestly, for a 2nd man-toy sort of plan, I'd actually suggest a previous generation Discovery like the 1996 with simpler technology and great off road. You can buy them so cheap even when you find a good one and mods are more DIY friendly. The Disco 2 has 6" more rear cargo length but it otherwise the same dimensions. People will go on about how the 4.6 had problems but the D1 I still have int he family has been a great vehicle for over 230,000 miles. Only recently has it started having some electrical issues but they are more annoyances than anything critical. A southern or western Disco (it's whole life) would be really good to start with.
With the plan to go to places with a bike and retain 4x4 trail capability, you could lighten the bike to something more easily put on an suv hitch. If you have ridden much, you also know that the lighter the trail bike, the more fun and nimble it becomes.