actually porting is where the holes are made bigger and polishing is smoothing the ports out to make the air flow more smoothly.
Now yes you can port and polish a diesel head. But if your going to do it you might as well make the valves bigger. You can also get a bigger cam to. But take into consideration this is not cheap to do. The parts are expensive because majority of the parts needed to build a diesel like this is going to be forged parts. Due to the high compression and heat that is made by a diesel your going to need strong parts.