Well, first off what kind of goals do you have for this tractor powerwise?
Stock turbo (more than likely a wore out TO4) isn't good for much more than 230 to 250hp so you can start there. Then you can move on to a set of bigger injectors; go with more than 4 holes (stock injectors and some cheap performance injectors are 4 hole). If you don't mind a little fabrication and don't plan on running it at the local pulls, installing an intercooler can also help.
Those are just simple places to start, I'm sure smokin binder will have more specifics for you, he seems to be our resident DT expert :Cheer: