I am in the process of putting a 4D56T into a 1988 b2600. I chose the 1988 because it supposed to be the easiest swap due to the fact it has a mitsubishi petrol engine in it already and shares engine mounts( I hope) late model 4d56T seems to be a bit different, see pics. The oil pan also can be swapped with some minor mods. Other modes include extending the oil pickup to suit the petrol oil pan which much be used to fit the diesel into the b2600.
More to come.
I also chose the Mazda because I have a 1993 Mazda B2600i extended cab which I love, but I have recently been bitten by the diesel smell, I mean bug!
after converting my Land Rover 90 to a diesel, I really wanted to do the same for my Mazda.