For a trip with more than one vehicle I prioritize field spares as follows from most to least important:
1. STEERING
2. STOPPING
3. RUNNING
4. COOLING
This may seem like simple stuff, but it's not.
Most people, including the ones in this thread get it backwards. They're all about having a starter or alternator and they have no TREs. If you have another vehicle to extract you (preferrably two) then all you really have to be able to do is steer. It won't be pretty with steering alone, but you will get out. Dealing with a vehicle that has lost steering is next to impossible. If you're still running around with stock steering links I hope it's just to the store and back. Tires go in with steering. Remember, tire failures are still the most common offroad issue. I can't believe how many people still don't carry valve stems. Rookies.
Braking comes next because if someone is doing the good deed of pulling you along miles of trail it's nice to be courteous enough not to run into them. This is where the Land Rover powertrain actually affords you an advantage. The t-case drum brake is a very good, completely secondary, system for stopping the truck. That said, once you take driveshafts, halfshafts and CVs out of the equation that capacity is diminished.
So think about that. A u-joint may not just help you go, it may help you stop.
Getting your truck to start and run comes well after those two unless you are alone. Within this category we can further order and separate what makes your truck run and what makes it run well. That's why a crank sensor beats out the IAC. A truck can be pretty unhappy and still drive down the trail, particularly in low-box. Furthermore if you're having a running issue, but the engine is turning, LET IT RUN. Don't go shutting the thing down to diagnose, unless you know have a hell of a hunch. Keep it going. This is especially true with a gasoline EFI fuel delivery issue. It may be angry, but if you shut it down you may not get it started again.
Your last priority is keeping the engine wet. Yes, even your POS sleeve-slipping Buick 215 aluminum V8 powerplant. The truck can run without any cooling capacity other than radiation if it has to. Not for long stretches, but you can limp it for months if you're careful.
If you want to be minimalist, stop thinking in terms of pounds and size and follow these guidelines to select only what you need to make it out. This is the KISS principle for fourwheel spares. It keeps the count low and the bulk is left to necessity.
That said, in a gasoline Land Rover I bring everything that could be helpful.
Why? Because this is no ultra high speed low drag machine. It's a Land Rover. It's 5,000lb plus vehicle. You think even 200lbs in spare parts is going to make the difference? It's not.
I don't bring all the spares imaginable because the truck HAS to have a VSS to run, but because a lot of this stuff will angry up your trip in a hurry. Furthermore, there are plenty of people who maintain their truck, bring along the minimum and then when they have an issue, turn around and go home.
I'm not into that. I'd much rather have the right spare and keep on rolling and complete my trip.
Think about that again.
If I have an extra CV I can keep right on going down the challenging route I set out to do. If I have a fuel pump I can keep driving under my own power. And if my TPS goes bad i'm not sweating whether I need to turn around and go back. I'm not averse to wrenching a little on the trail. In fact, despite the lack of a lift and clean floor I enjoy it. I'd rather be out somewhere remote and beautiful changing a CV than limping back home to do it at the shop.
It's part of the fun.
