This isn’t one of those 4.2 blocks with the problem studs? They talk about those a lot on the XK-engine forum.
Keep oiling the studs with Kroil or Liquid Wrench or whatever is your favorite penetrant.
The engine hoist is best if you can get slings around a couple of intake and a couple of exhaust studs, the idea being even loading. Give it some up force and let it hang awhile. Tap on the top end of each stud with a large flat end punch and 2 lb. ball peen hammer, the idea being to give the rust some resonant shock.
The idea of the wood block above the bottle jack is to distribute the load over a larger area, as opposed to just the top flange of the jack.
Don’t go crazy with the jack, because it only loads one side, just give it some force and let it sit awhile.
You could try the hoist and jack together, alternating jack, no jack, jack, no jack, etc.
I had a stuck head on a 140 engine my brother found in a field. It had been sitting there so long the head valley was full of dirt from decaying leaves. It took me about a month of soaking with oil and up force with the hoist and tapping on the studs before it came loose.