If the bolt doesn't fit the socket that should fit it. Then I would probably just cut it off & replace the bolt with a new one.
Or weld a nut onto the bolt head? Heat from welding can help!
Not had an issue personally
Someone on here built on of the kit heaters a couple of years ago but I can not remember who it was.Don't know if it is worth the £30 + to have experiment for a Chinese kit, any one tried them ?
I have a set of Irwin removers, absolutely magic when you’ve rounded the bolt heads/nuts as inevitably happens. Only down side is mine are 3/8th drive rather than 1/2”. Paraffin & diesel makes a good penatrating oil, paraffin gets in anywhere & diesel provides lubrication.You want the irwin ones. They come in a set plus expansion set too. You'll never look back after using them
Sockets no good when you have wound the head off easing oil & heat will hopefully remove the threaded bit with head still on, blasting the threads will also help.
Wish I had found the induction heaters whilst still working on the vintage classics.
Adjustable's an Invention of the Devil