B&Q do a stone grinding kit for a regular drill, £4.99 and some engineers blue (marker) £1.50.
Set the gaskets over the ports, mark the excess metal with the engineers blue and then go nuts with the grinding stones. A couple of hours will port the inlets upper and lower. Just grind them out to almost out to match the gaskets. It's cheap and easy and gave me something to do in the garage when I couldn't be arsed getting dirty.
EDIT: Just realised the age of this thread ffs.