aluminum head corroded stud

got a budi with a aluminium head, Nissan exterra his family car with a broken intake stud, broke off in it ...it's the typical corrosion you get when mixing metals like that .
his mechanic has, "probably not certified" has tried heating it reattaching a head on the bolt and it wont come out he's going to attempt to drill it out, but already dulled 2 carbide bit's. i'm trying to get pic's haven't seen it he's just trying to describe it to me,
what are your suggestions on how tow get it out
the head is on the motor it was pulled for a supposed head-gasket failure.
our tried and true was to heat the head or block with a propane torch, and hit the bolt with r 12, now today...134 a it works for us
how would you get it out?
Author: Gorts 5th