More than 50 years ago, I had this problem on my Comet – exhaust thread completely gone – I bored the head out to take a thin walled shrunk in threaded insert made from duraluminium – I’ve still got the old girl and the repair is still good today.
I would however strongly recommend shrink fitting an insert rather than press fitting because well documented experimental work on shrink fits vs pressed fits has shown that a shrink fit has something like three times the ''grip''.
Such work requires a cryogenic source; liquid Nitrogen is the obvious choice but if not available then a mixture of solid CO2 (Cardice) in Acetone is also pretty cold (-77°C) and might be more easily obtained.
A lot of work? Maybe, it certainly requires more facilities than the average owner will have so farming the job out would seem to be the way to go. However, this method has the merit that it imposes almost no thermal stress on the cylinder head, is all but invisible and it worked!