This is just my opinion of course.
I have done several head gaskets on 4.6 Range Rovers, as yet not one 4.0.
I also would not change the suspension over to coil springs. When the airbags start to leak, people for some reason leave them leaking. This then makes your compressor work all the time, this then becomes an expensive job unless of course you have or know where to get secondhand parts

I think the airbags are a doddle to fit (although making a tool to remove the back ones pays dividends) and cost about £70 each brand new.
Your right about the gas tanks, so would to put them elsewhere. Saw a good one with a half sized fuel tank so an lpg tank filled the other half, also tanks in between the boot panels and rear quarter if that makes sense so the boot space and 7th seats were not effected.
As for miles per gallon, if you get 20 on a run I think your doing well, about 16 knocking about. But if you tow a caravan you will still get 20 on a run like we did.
Disco's you will have to do the small springs in the locks at sometime, as when you pull the outer handle to open the door the inner pully knob drops down... So dont leave it running and close the door like I did

. They cost about £5 to buy and a day full of moaning and swearing to fit them.
I personally like the v8, prefer the Range Rover myself but Mrs. Loo-knee loves her Disco. Take it off roading though mate, its a must. They get where you would not believe, would not wade to deep with a v8 mind

enough for water to come though the door rubber though

I am sure you will be happy with your £1000 buy
