I'm doing this right now on my M104 because my oil pump decided to blow up.
The diesel oil pump and the M104 oil pumps are exactly the same. The only difference between the two are the sprocket's that drive the oil pump via the oil pump chain. Mercedes doesn't sell the stock oil pump sprocket anymore, so now, the only sprocket you can buy for the M103, M104 and OM603 are the diesel 603 part # sprockets.
So, just buy the stock oil pump and sprocket and you'll have your diesel oil pump no matter what. The pumps already pump about 35psi of oil pressure at 2k rpm, what more do you need? All it takes is 3psi of pressure to get the oil from the bottom up top, the rest is volume which is plenty enough already.