Cheapest 4.6L I saw on eBay was $1400 plus shipping from a guy with 0 feedback. Yeah, I'll take two. The going price for a Bosch 4.6L is over $2K on eBay these days when you factor in shipping.

The OP's price of $4K for a long block, installed depends on a lot of information we've not been given. Are we talking about a new 4.0L long block or one form a questionable seller offering a dodgy shortblock for a few hundred dollars? Are we talking about paying a full service Land Rover specialist to do the installation of a motor they sourced, complete with warranty or are we talking about a long block from the junkyard you want to install with the help of your neighbor? Frankly, at this point, with the value of DII's being what they are, it's really tough to justify the expense of a replacement engine unless you are absolutely head over heels with your truck, have money to burn or are prepared to do most of the labor yourself. Most people barely fall into a single one of these categories let along a majority of them.