You wouldn't need a turbo with the extra grunt it has but alas the weight would be the biggest problem. I have thought hard about doing it.
Printable View
Here's a Series III fitted with a 1987 Isuzu diesel and 5 speed box on eBay. You'd probably want to take a close look at the quality of the conversion before making an offer.
Landrover Series 3 diesel wagon with later motor and transmission | eBay
I came across these on carsales.
Stage 1
County with some Fruit
A mate of ours test drove that county. Said it was the most unstable and scariest thing he has driven!!!!
Justin
I think the seller of the blue County is a member here. From the description it does have a lot of fruit!