The head needs to come off for a good visual.
Bluestream. Maybe elaborate on your statement and tell the "benefits" of the leakdown.
If the motor had valves? I'd agree with you.
Did the broken bolts come out or they still in?
Removing the bolts.
PB Blaster, Krol, or any penetrating liquid a torch and a couple pry bars.
Spray and heat the studs a bunch
Then try to insert the prybars and work the head off the studs. Try to do as little damage as possible to the
mating surfaces. Damage to the block can be hard fixing. The head can be welded fairly easy.
The reason they broke is the corrosion from dissimilar metals close or touching each other.
Every time the motor gets .hot the corrosion gets a tiny bit worse.
When you reinstall, marine grease.
The trying to blow the head off probably won't work.