Denny's idea is the way to go. The way I did it is always the 'other way' which is drill out the existing stud but use a tap drill and drill for a 10-32 tap. Then turn a longer screw from underneath clear up until the head is flush, then since I do not trust that flimsy metal to keep the screw in, put a 10-32 square nut over the top to sandwich it all together so there is no chance of the screw or hardware dropping down into your precious engine. I haven't checked McMaster-Carr to see if they have the standoffs that Denny made by hand that would fit and be long enough, but its a possibility. They surprise me a lot.
