...takes more volume to spool up. Unlike the gassers, Diesels are RPM limited by the nature of the beast. It is true with modern technology we can get our 2.8L to rev up to 4,000 in stock mode with out sending all of the rods out the side of the block, but there is a limiting factor on how fast the injectors can fire and make things go. Many Years ago Mercedes got one of their diesels to crank up to 6,000 RPM before the era of the Common Rail, but this took a lot of work and the application was limited to the test track. Gas fuel injected engines of that era were cranking 10,000 on some of the test tracks.
With the Quest of the ORT related technology, they all discovered going after TORQUE was more cost effective and produced better results along with better fuel economy. From this school of thought, many of the current production diesel engines evolved including our CRDs.
In order to make a larger turbo work well, you would need to have a way to generate more exhaust flow by going to larger ports, larger valves, larger exhaust manifold or very elaborate headers, larger intake, higher flow injectors, and hope the block, rods, and crank are strong enough to handle the extra torque. If you are ready to machine your own crank out of a 4140 forged billet, harden it, temper it, grind it, and balance it, knock your self out

Rods will also need to be machined out of 4140 but you may be able to get away with half-hard and skip the heat treating process.
The best way to convert the 2.8L into a diesel racing engine would be to scrap the ECM and start over from scratch with your own logic using the Bosch logic as a guide line. Then hook up a bunch of sensors and push a test engine to the point of failure
Before you do all of that, read up on turbochargers and how to hot rod engines, books are a cheaper way to learn than destroying engines. When you have a good sized stack of books you have read and re-read you are ready to go beyond stock.