Hiya.
I have had a Land Rover naturally aspirated 2.5 lump in my boat for the last eleven years. It's very reliable, if a little basic and agricultural. There are two sorts of these engines, the earlier 3 bearing and the later 5 bearing - the code to look for is 19J. There is also a small difference in the front timing cover between a Land Rover one and a Sherpa one.
In terms of reliability, my engine did about 250,000 miles in a Sherpa van and a Land Rover before I put it in the boat. The biggest drawback in my view is that they are not very economical and they do need solid engine mounts as they are not very smooth.
I found it very easy to obtain a second hand Bowman marinising kit, comprising bell housing, engine mounts and heat exchanger. I was told that some BW workboats were fitted with these engines at one point, hence Bowman going to the trouble of making a kit. It runs a PRM 260 with no problems at all.
BG