Incorrectly installed Cleveland gaskets, or even worse, Windsor gaskets on a Cleveland, are a real issue and could likely be the cause of your boiling and gurgling
yes, you can remove the iron heads with the engine still in the car. I have done it alone when I was younger. Much easier if you have a helping hand. Lay out a lot of towels and blankets for positioning and moving until you can lift it out of the engine bay. I understand if the heads are mounted on studs rather than with bolts it is more difficult but I still believe it can be done.
an infrared temperature gun from Harbor freight or similar might help with your diagnosis
good luck
Larry