One way you could try is to put a piece of say 1" O.D. ali in your chuck. Using say a 1/2" drill, just drill the pointy bit on the end depth, don't start cutting the straight part. DO NOT use a centre drill, it will be the wrong angle, but do use a centre drill first to give clearance for the large flat on the big drill end. If the centre drill hole is not big enough, measure across the flat and go in a bit with a drill just a little larger.
Now mount up the big drill with the pointy end into the cone you have just cut and bring in your tailstock centre to the 'pip' in the back. Now gently start cutting away at the morse taper, and as the large drill starts to bite into the ali, tweak up the tailstock centre. Once it gets so far, it won't want to dig in any more, and if you are careful and don't take heavy cuts, you should be able to turn the taper to parallel.
Another way would be to bore and make a split collar so that you could hold the drill flutes in a normal chuck.
Hope you understood that.
Bogs