OK, I'm not proud of this, but here it goes. I had exactly the same problem with my 123GT. Tried for days, no dice. So I buttoned it back up, and drove it to the local muffler/brake chain store for a "Free Brake Inspection". They laboured all day, broke their puller, brought in a slide hammer from another store, used the torch, etc., and finally got it loose. I felt so guilty that I paid them to install the parts that I had already assembled. Still, I'm sure I'll go to hell for this. I did put anti-sieze compound on the half-shafts, and haven't had a problem since.