I agree, When I was running my V8 in the USA the cost of fuel was so cheap it was silly. I imagine the price has probably gone down since then as well.
There are not many V8 Defenders, the factory standardised on the Tdi at some time around 1994, after that the V8 was only available as a special order.
One good thing about pretty much any V8 is that they will probably be lower mileage than a contemporary coal burner. It is worth a look on Ebay, both in the US and UK, reasonable V8s seem to pop up quite frequently, though beware, there are some really nasty ones offered as well