Originally Posted by 
Graeme
				
			 
			The early alloy 3.0 rear calipers had blobs of metal protruding out the ends for no apparent reason other than to block the fitment of 18" rims but were later replaced with the D3's smaller, strictly functional cast iron calipers that allow 18" rims to fit (same as the V8 D3), presumably because the alloy calipers caused squealing in reverse when dusty.
The 2 centre ribs on the front calipers protrude further out than the end 2 ribs. If a person is prepared to make the modification, the centre hump of these 2 ribs can be reduced a couple of mm to allow 18" rims to fit.  IMO this is a better proposition these days than fitting 2.7 brakes to allow 17" rims due to the range of 18" tyres now available and that LR 18" rims now fit the rear.