Would you remove/replace these studs?

[pavilla]

After my water pump debacle (other thread today), I'm skittish about removing the studs on my Model B 4 cyl head. I squirted them with rust buster about 6 times over several days, then put an induction tool on one of the studs, heated it for about a minute. The base of the stud was glowing red-hot. Let it cool, tried the two-nut method of backing it out. No go. Another heat/cool cycle. Tried a pipe wrench with a good amount of torque. Nothing. After breaking the shaft on my water pump, I'm wondering if it is worth the risk here of breaking studs. The existing studs are rusty, but the threads seem okay. I don't know the history on the engine, but I am guessing these are not original studs. I can weld if need be, but if these studs are so stuck that they break, I don't have a lot of faith that welding a nut on a broken stud is going to be the solution. And drilling these out is not something I want to get into. I suppose I could try other studs and replace any that I can get out. And, just how long should I heat the stud with the induction tool? At less than a minute, the bottom half inch or so of the stud seems to be red hot. What is too much heat? Thoughts? Thanks.