I just finished redrilling my front hubs to 4.5" bolt pattern. I haven't got the rears off yet but they're next so I can let you know how it goes.
The problem I had with the fronts was that between the existing stud holes there is no flat surface for the head of the stud. What I did was to weld some metal to the back of the hub, then machine it flat to match where the existing stud holes are, then I drilled the new holes. Seems simple enough but the weld was VERY hard metal and I destroyed a new drill bit, then bought a Cobalt drill bit and some Tap Magic and drilled reeeely slow. I destroyed the Cobalt drill bit too but not before it got the job done.
Hopefully I can just redrill the rears without having to weld.
Another thing I did was to switch to the Mustang studs. They are a bit larger in the knurled diameter. I had to switch to them because the shouldered nuts that go on Weld wheels come in 1/2", not in Tbird metric.
About halfway through the ordeal I checked with a machine shop and they said they would do all 4 for $150. If I hadn't invested in 2 drill bits and a lot of work already, I would have just had them do it.