[acshortt5]

Gutted for you.

My thoughts would be that if you can get it out of the car so access is not a problem I would remove the stud and retap the thread in the head (or get a machine shop to do it for you). Then install a new stud to be on the safe side. If you are lucky just (slowly and gradually) working the tap in and out might clean it up and sort it.

A potential bodge would be to remove the stud and measure the length you've got where it will screw in and either use a shorter stud or a bolt of suitable length - you could even get a bolt with the head drilled so that you could run lockwire through it to stop it from rotating/backing out.
Depends on where the damage to the thread is - if it's just in from the start then a bodge will be too risky. If it's deep into the block then there's less risk.

When I was doing my turbo I removed the manifold to replace it (engine still in the car) and I had one or two studs come out. They got replaced by new volvo studs and they went in easy - I didn't use the volvo nuts to install because as you've said they are SERIOUS locknuts and the studs don't really have anywhere to get a proper grip without risking damage to the threads.

I had to retap both threads on the turbo and one on the exhaust manifold collector but they were spare parts I was preparing in advance of the work to swap them over so not as big a deal for me, still a PITA but that's ebay "good condition" for you...

The studs and nuts from volvo are seriously expensive - I think because they might be made from inconel - the nuts anyway.
Locktite will do sod all as I think the temperature will be too high - tried that on some nuts on my exhaust downpipe on my mx5 (non turbo) and it worked initially until it melted - I ended up using aerospace spec nuts/bolts which sorted it but for £££'s.

Tip - use a V50 T5 exhaust manifold gasket as it's a single piece (much easier to fit) and (for me at the time) was considerably cheaper than buying the 5 single gaskets.