While I've never experienced this with a Rover... I'd be cautious with wheel spacers. Some guys I race with use them on their race cars to fit wider slicks in the wheel well. Almost all of them ended up blowing wheel bearings or in my case the load actually cracked the entire hub. I know we're not talking about the same level of abuse but ever since I saw that, I've been weary of adding spacers due to the potential stress it places on the bearings and wheel assembly.
Land Rovers are by far the best looking 4x4 on the back of a flatbed...