I would keep the turbo. My SIII with overdrive, higher ratio diffs and 109" front axle, was a pleasure to drive on motorways after changing the diffs.
I think that there may be another good reason to keep it, but I'm happy to be corrected. The turbo has a thin pipe that connects to a t piece and then on to the fuel pump and wastegate. It's job is partly to tell the fuel pump to deliver more fuel once a certain boost pressure arrives. My hunch is that the pump is designed for the turbo engine and won't deliver enough fuel at higher revs without that signal. So you'll not only be down on power without the boost, but also through under supply of fuel. That could be utter bollocks, but when the pipe split on mine, that lack of extra fuel crippled it.
Although I'm very techy, I haven't looked into it because I loathe diesel engines in cars. My project car is going to be petrol powered, so I'll never need to know how a diesel fuel system works!