Im guessing you're in Oman already, in which case you're in a tricky spot to get out of.
Saudi Arabia, my friends who've been there say travel is "arduous", mainly due to social factors. The main sights are mecca and medina which are closed to non-muslims, but driving the empty quarter would be an extraordinary challenge of thats what your up for.
Shipping across to Iran is probably easier, and you get to see Shiraz, Esfehan, Qoms, Tehran as well as persepolis and depending on your route, and if you're not wedded to Tehran, then the Darius inscription as well.
Heading out of Iran you can go via Azerbiajan/Armenia which could be a bit tricky military/land mines/hostile police etc, but possibly worth it. Georgia is accessible from this route, coming from the south but these countries have been in the news for the wrong reasons lately. Apparently good travelling, though.
An easier path may be via Lake Van (Which I missed last time I was in turkiye, dammit) home of the Van cats, and some pretty awesome sights.
Depending on where you want to go, a border crossing is available near Antakya into Syria which is WELL worth the time, with Krak de Chevaliers, palmyra and damascus which has some very interesting history. Perhaps a conversion on the road of some sort ?
This route will allow you into Jordan, and Lebanon (safe-mostly, and extremely interesting place), as well as Israel (watch for visa stamps) maybe Egypt.
If you want to continue touring Turkey you can ship on a ferry past Crete to a turkish port, but services are extremely variable last I heard.
Europe Im sure you can work out, the Americas I dont know well, except I can recommend some AMAZING restaurants in Mexico city

James

Look up this site Kookynet.net: The Kooky Project: culinary adventures around the world
Robert & Martine did similar and are friends with many of us on this site. A lot of us had them stay with us when travelling through OZ. They had an awesome Defender called Allistair before it was destroyed in transit.
I would be looking at your route and determining what LR service and parts agents are available. Last thing you want to take is too much useless gear. I would also try and develop a relationship with a good LR parts supplier, that can air freight you parts when you need them anywhere in the world. Easier to do before you leave and they know who you are, than ringing them from some obscure part of the world.
As said
Cooling Hoses
Serpentine Belt
Turbo hoses
Sensors and ECU(good idea but are they really neccessary to carry as spares and at what expense)?
At least one of every filter.
4 or 5 litres of engine oil (should be readily available enroute).
2 litres of gearbox oil.
2 litres trans case / diff oil. 1 litre laboratory sample bottles are great for this.
4litres coolant concentrate.
Being a TD5 an injector harness.
Wheel bearings, grease and hub spanner.
Spare sump plug and crush washers.
Adequate tools.
Puncture repair kit.
Recovery gear.
At least dual batteries, maybe even a solar panel.
Plus all your gear needed to eat and sleep.
Sounds like a great trip.
Cheers
Craig

__________________
2000 Defender Extreme : AKA Toyota Recovery Vehicle / Green Pig / Shrek
1976 SS Torana (due for restoration)
1998 Ducati 900SS (Feel The V-Twin Roar)
1984 RR (Gone). 1997 Tdi Disco (Gone)
Facta Non Verba

Hi there,

Lebanon is the place to visit, if you intend to do it, I will more than happy to help.

Do not worry for spare parts as Land Rovers are a common sight in Lebanon thus spare parts are available.

I can offer also a safe heaven with a good workshop.

Please do not hesitate.

Have a safe trip
Patrick

I would suggest to you to be a member of the PORTAL.
The information there about expeditions is awesome and few members have Defenders including some of the moderators.
I am a member and I found the Portal among the best forums in the net.
Cheers